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Klik på et bogstav for at se de begreber, der er forklaringer til.
- ACE-hæmmere: Angiotensin Converting Enzyme hæmmere. ACE-hæmmere nedsætter aktiviteten af renin-angiotensin-aldosteron-systemet ved at hæmme omdannelsen af angiotensin I til II, hvorved universel vasodilatation uden sympatikusaktivering indtræder og medfører fald i blodtrykket. Anvendes typisk mod forhøjet blodtryk og hjerteinsufficiens.
- Antacida: Stoffer der neutraliserer syre produceret i mavesækken. Eller: Syreneutraliserende stoffer, der medfører neutralisering af mavesækkens pH.
- AUC: Area under the curve. Det grafiske areal under en plasmakoncentrations-tids-kurve for et lægemiddel. AUC bruges til at beskrive, hvordan kroppen eksponeres for et givent lægemiddel og anvendes til at estimere biotilgængeligheden og clearence.
- BID: Medicinsk forkortelse for bis in die = to gange dagligt.
- Biotilgængelighed, F: Den del af et oralt administreret lægemiddel, der i forhold til en intravenøs dosis når det systemiske kredsløb. Omfatter også den hastighed, hvormed dette sker. Biotilgængelighed omfatter både absorptionen over tarmvæggen (absorptionen sensu strictiori) og en evt. førstepassagemetabolisme.
- Bredspektret antibiotika: Antibiotika med virkning på et bredt spektrum af mikroorganismer, i modsætning til smalspektrede antibiotika, der kun er virksomme over for specifikke typer af mikroorganismer.
- Clearance (Cl): Forholdet mellem et lægemiddels (eller andet stofs) eliminationshastighed (mængde per tidsenhed) og dets koncentration i plasma (eller blod).
Clearance er konstant, dvs. koncentrations-uafhængig, for stoffer, der elimineres efter en 1. ordens-reaktion. Clearance bestemmer sammen med fordelingsrummet halveringstiden. Clearance fra forskellige eliminationsorganer er additiv.
- Cmax: Den maksimale koncentration i plasma, der opnås efter lægemiddelindgift.
Ved i.v. indgift er Cmax lig Co, mens Cmax efter peroral indgift oftest først opnås efter 1-2 timer (tmax).
- CYP P450: Cytochrom-P450. Enzymsystem, som metaboliserer adskillige lægemidler via oxidering.
Oxidering udgør den kvantitativt dominerende eliminationsvej for lægemidler. CYP-enzymerne forekommer i særlig høj koncentration i leveren.
- Fald i clearance: Lægemidlet tager længere tid at få renset ud af kroppen.
- Halveringstid, t1/2: Den tid, det tager organismen (efter fordeling) at eliminere halvdelen af den tilbageværende mængde lægemiddel i kroppen.
Størrelsen er konstant og koncentrationsuafhængig for lægemidler med 1. ordens-elimination.
- Hepatisk: Vedr. leveren.
- Hypertension: Forhøjet blodtryk.
- Hypoglykæmi: Lavt blodsukker. Symptomer optræder ofte ved blodsukker lavere end 2,5 mmol/L.
- Hypotension: Lavt blodtryk.
- Hypothyreose: Nedsat funktion af skjoldbruskkirtlen som fører til nedsat dannelse af hormon (thyroxin) og dermed for lavt stofskifte.

- Inducerende lægemiddel: Når et lægemiddel forårsager øget omsætning af et andet lægemiddel via induktion af f.eks. CYP450.
- Induktion: Øget omsætning af et lægemiddel via induktion af f.eks. CYP450.
- INR: International normalized ratio. INR er en standardiseringsmetode til sammenligning af koagulationstider (protrombintider, PT). INR er således et mål for blodets evne til at koagulere.
INR har til formål at minimere forskellene mellem tromboplastinreagenser ved hjælp af en kalibreringsproces, hvor alle kommercielle tromboplastiner sammenlignes med et internationalt referencemateriale. INR beregnes således: INR=((Patient PT)/(Middel normal PT))^ISI , og fortæller dermed hvor lang koagulationstiden er i forhold til den normale koagulationstid.
- ISI: International Sensitivity Index. Protrombintid målt med forskellige tromboplastiner kan ikke sammenlignes direkte med hinanden, f.eks. fordi sensitiviteten over for koagulationsfaktorer kan variere. For at få koagulationstider, der er så sammenlignelige som muligt, godkendte Verdenssundhedsorganisationen (WHO) i 1983 en standard reference-tromboplastin. Alle producenter af tromboplastin skal kalibrere deres reagens over for WHOs standard. Den fundne værdi betegnes International Sensitivity Index (ISI), og bruges til at beregne INR.
- Iskæmi: Ophævet eller nedsat blodforsyning af et væv i forhold til dets behov.
- Isoenzymer: Forskellige udtryksformer for et enzym. Opstår pga. af forskellige allelle gener. Eksempler ses inden for det lægemiddelomsættende system CYP450, hvor isoenzymer f.eks. er 2D6, 3A4 og 2C9.
- Kasuistik: I lægevidenskab en offentliggjort beskrivelse af et enkelt eller få sygdomstilfælde (casus (lat.): ”tilfælde, sag”).
- Lipidsænkende lægemidler: Lægemidler, der sænker visse af blodets fedtstoffer – kolesterolsænkende.
- Metabolisme: Metabolisme eller stofskifte er en generel betegnelse for den biokemiske omsætning af kemiske forbindelser i den levende organisme og dens celler. Bruges synonymt med biotransformation.
- P-gp: Permeability glycoprotein. P-gp er et cellemembran-protein, som er tilstede i epithelceller i bl.a. tarm, lever og nyrer, hvor det transporterer fremmede substanser fra blodet og ud i hhv. tarmen, galdegange og nyretubuli.
- Plasma: Plasma er den fraktion af blodet, der ikke indeholder celler. Plasma indeholder forskellige næringsstoffer, hormoner, antistoffer, koagulationsfaktorer og salte. 95% af plasma består af vand.
- PO: Per os. Via munden.
- PN medicinering: Pro re nata medicinering. Medicin, der gives efter behov.
- PT: Protrombintid. Tiden, det tager plasma at koagulere, efter tilsætning af tromboplastin (også kaldet tissue factor). Protrombintiden bruges til at vurdere blodets koagulationsevne, og anvendes især til monitorering af antikoagulationsbehandling.
- qd: Quaque die. Hver dag.
- QID: Quater in die. Fire gange dagligt.
- Renal: (af lat. renalis), vedr. nyrerne.
- Respirationsdepression: Respirationsdepression (også kaldet hypoventilation) er når frekvensen eller dybden af respirationen er utiltrækkelig til at opretholde den nødvendige gasudveksling i lungerne.
- Serotonergt syndrom: Et symptomkompleks, der skyldes overstimulering i centralnervesystemet med serotonergt aktive substanser. Symptomerne er muskelrykninger, skælven, kvalme, diarré, sved og forvirring.
- Serum: Plasma uden koagulationsfaktorer.
- SID: Semel in die. Én gang dagligt.
- SmPC: SmPC står for Summary of Product Characteristics, og er det engelske udtryk for produktresumé.
- TID: Ter in die. Tre gange dagligt.
- tmax: Det tidspunkt, hvor den maksimale plasmakoncentration af et lægemiddel indtræder. Des hurtigere absorptionshastighed, des mindre tmax.
- Total clearance: Summen af hepatisk og renal clearance. I hvilken grad disse fraktioner bidrager afhænger af, om lægemidlet primært udskilles renalt eller også undergår fase I (f.eks. via CYP) og fase II (f.eks. glukuronidering) biotransformation i leveren.
- UGT: Uridine 5'-diphospho-glucuronosyltransferase, eller UDP- glucuronosyltransferase. Glucuronyltransferaser er enzymer, som foretager konjugering (glucuronidering) af mange lægemidler og lægemiddelmetabolitter, hvorved de omdannes til stoffer, der er lettere at udskille.
- Vasodilatation: Udvidelse af kar.
- Vasokonstriktion: Sammentrækning af kar.
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Formålet med Interaktionsdatabasen er at gøre behandlingen med lægemidler mere effektiv og sikker, og fremme kvaliteten i patientbehandlingen, herunder bidrage til rationel farmakoterapi. Det har været til hensigt at udvikle et redskab, der er let at anvende i den kliniske hverdag og, hvor der på højt fagligt niveau er skabt konsensus om rekommandationer og beskrivelser af interaktioner mellem lægemidler.
Interaktionsdatabasens primære evidensgrundlag er offentligt publicerede, peer-reviewed original interaktionslitteratur (kliniske studier udført på mennesker og kasuistikker) publiceret i PubMed og Embase.
Der vil således kunne forekomme uoverensstemmelse mellem andre opslagsværker, som er opbygget efter andre principper og evidenskriterier.
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Etableringen af Interaktionsdatabasen var et fælles projekt mellem Danmarks Apotekerforening, Den Almindelige Danske Lægeforening, Dansk Lægemiddel Information A/S og Institut for Rationel Farmakoterapi. En projektleder og 2 farmaceuter stod for opbygningen af databasen bistået af et fagligt videnskabeligt udvalg. Desuden har der været tilknyttet eksperter indenfor forskellige fagområder. Efter en årrække under Sundhedsstyrelsen overtog Lægemiddelstyrelsen i 2015 driften og vedligeholdelsen af databasen.
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Vær opmærksom på, at alle anbefalinger på Interaktionsdatabasen.dk er vejledende.
Hjemmesiden giver desuden ikke oplysninger om bivirkninger ved hvert enkelt præparat. Her henviser vi til indlægssedlen i det enkelte præparat eller til Lægemiddelstyrelsens produktresuméer.
Der kan forekomme bivirkninger, du ikke kan finde informationer om her. Dem vil vi opfordre dig til at indberette til Lægemiddelstyrelsen. Det kan du gøre på:
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I denne database er lægemiddelinteraktion defineret som en ændring i enten farmakodynamikken og/eller farmakokinetikken af et lægemiddel forårsaget af samtidig behandling med et andet lægemiddel.
Interaktionsdatabasen medtager farmakodynamiske interaktioner, der ikke er umiddelbart indlysende additive (fx med forskellig virkningsmekanisme), og som kan have væsentlig klinisk betydning.
Andre faktorer, som interagerer med eller ændrer lægemiddelvirkningen så som næringsmidler (f.eks. fødemidler og kosttilskud) og nydelsesmidler (f.eks. alkohol og tobak), er ikke medtaget. Dog er medtaget lægemiddelinteraktioner med grapefrugtjuice, tranebærjuice og visse naturlægemidler.
Interaktionsdatabasens primære evidensgrundlag er offentligt publicerede, peer-reviewed original interaktionslitteratur (kliniske studier udført på mennesker samt kasuistikker) publiceret i PubMed og Embase. Desuden er interaktioner hvor data er beskrevet i produktresuméer medtaget.
I Interaktionsdatabasen findes fem forskellige symboler:
- Det røde symbol (tommelfingeren, der peger nedad) betyder, at den pågældende præparatkombination bør undgås. Denne anbefaling bliver givet i tilfælde hvor det vurderes, at den kliniske betydning er udtalt, og hvor dosisjustering ikke er mulig, eller hvis der er ligeværdige alternativer til et eller begge af de interagerende stoffer. Det røde symbol vælges også i tilfælde, hvor der vurderes at være ringe dokumenteret effekt af et eller begge stoffer, (hvor anvendelse derfor ikke findes strengt nødvendig), f.eks. for visse naturlægemidler.
- Det gule symbol (den løftede pegefinger) betyder, at kombinationen kan anvendes under visse forholdsregler. Denne anbefaling gives i tilfælde, hvor det vurderes, at den kliniske betydning er moderat til udtalt, samtidig med at den negative kliniske effekt af interaktionen kan modvirkes, enten gennem ned- eller opjustering af dosis, eller ved at forskyde indtagelsestidspunktet for det ene præparat. Anbefalingen gives også, hvis det vurderes, at kombinationen kan anvendes under forudsætning af øget opmærksomhed på effekt og/eller bivirkninger.
- Det grønne symbol (tommelfingeren, der peger opad) betyder, at kombinationen kan anvendes. Denne anbefaling gives i tilfælde, hvor det vurderes, at den kliniske betydning er uvæsentlig eller ikke tilstede.
- Det blå symbol (udråbstegnet) fremkommer i tilfælde, hvor der søges på et specifikt præparat eller en præparatkombination, som ikke findes beskrevet i Interaktionsdatabasen, men hvor der findes andre beskrevne interaktioner mellem stoffer i stofgruppen, som muligvis kan være relevante for søgningen.
- Det grå symbol (spørgsmålstegnet) fremkommer i tilfælde, hvor der er søgt på et præparat eller en præparatkombination, som (endnu) ikke er beskrevet i Interaktionsdatabasen, og hvor der heller ikke findes beskrivelser af andre præparatkombinationer mellem de to stofgrupper. En manglende beskrivelse er ensbetydende med, at Lægemiddelstyrelsen ikke har kendskab til videnskabelige undersøgelser, der undersøger en interaktion mellem den pågældende præparatkombination, og heller ikke til kasuistiske beskrivelser af en mulig interaktion. Der kan også være tale om en kombination, hvor der ikke kan drages konklusioner på baggrund af nuværende viden.
Opdatering af databasens faglige indhold foregår via litteratursøgninger som leveres via Det Kongelige Bibliotek. Litteratursøgningerne er struktureret efter veldefinerede søgekriterier og bliver løbende evalueret. Endvidere foretages yderligere håndsøgning i referencelister som kvalitetssikring af litteratursøgningerne.
Databasen bliver opdateret løbende.
Lægemiddelstyrelsens enhed Regulatorisk & Generel Medicin står for opdatering og vedligehold af Interaktionsdatabasens indhold.
Vedligehold og opdatering af databasen foretages af den faglige arbejdsgruppe, som består af 1 akademisk medarbejder og 2 studerende.
Arbejdsgruppen samarbejder med en deltidsansat speciallæge i klinisk farmakologi omkring den kliniske vurdering af lægemiddelinteraktionerne.
Interaktionsdatabasen er et opslagsværktøj, der beskriver evidensbaserede interaktioner, det vil sige interaktioner, der er dokumenteret ved publicerede kliniske studier og/eller kasuistikker. Der vil således kunne forekomme uoverensstemmelse mellem andre opslagsværker, som er opbygget efter andre principper og evidenskriterier.
Der inkluderes kun interaktioner fra offentligt publicerede, peer-reviewed original interaktionslitteratur (kliniske studier udført på mennesker samt kasuistikker) publiceret i PubMed og Embase. Desuden er interaktioner hvor data er beskrevet i produktresuméer også medtaget. Det tilstræbes at databasen opdateres snarest efter publicering, men der kan forekomme forsinkelser.
Interaktionsdatabasen beskriver interaktioner for markedsførte lægemidler, naturlægemidler samt stærke vitaminer og mineraler. I interaktionsbeskrivelserne skelnes som udgangspunkt ikke mellem forskellige dispenseringsformer. For udvalgte lægemidler skelnes dog mellem dermatologiske og systemiske formuleringer. Handelsnavnene for stærke vitaminer og mineraler, naturlægemidler samt lægemidler som ikke figurerer på medicinpriser.dk (dvs. SAD præparater) kan ikke findes på interaktionsdatabasen.
Interaktionsdatabasen omhandler ikke kosttilskud, vacciner, parenteral ernæring, elektrolytvæsker, lægemidler uden systemisk effekt og priktest (ALK).
Ja, du kan slå både lægemidler, naturlægemidler, stærke vitaminer, mineraler og enkelte frugtjuice op.
Naturlægemidler er en særlig gruppe lægemidler, der typisk indeholder tørrede planter eller plantedele, udtræk af planter eller andre naturligt forekommende bestanddele. Naturlægemidler er i lovgivningen defineret som "lægemidler, hvis indholdsstoffer udelukkende er naturligt forekommende stoffer i koncentrationer, der ikke er væsentligt større end dem, hvori de forekommer i naturen". Naturlægemidler skal godkendes af Lægemiddelstyrelsen inden de må sælges.
Stærke vitaminer og mineraler er en gruppe lægemidler, hvis indholdsstoffer udelukkende er vitaminer og/eller mineraler, og hvor indholdet af vitamin eller mineral er væsentligt højere end det normale døgnbehov hos voksne mennesker. Stærke vitaminer og mineraler kan kun godkendes til at forebygge og helbrede såkaldte mangeltilstande (og altså ikke til at behandle sygdomme). Stærke vitaminer og mineraler må kun sælges i Danmark, hvis de er godkendt af Lægemiddelstyrelsen.
Ja, du kan søge på så mange lægemidler/indholdsstoffer, du ønsker samtidig. Det gør du ved at bruge søgeboksen til højre på forsiden med overskriften ”Søg på flere præparater i kombination”. Her kan du tilføje flere felter med knappen nederst. Hvis du søger på kombinationer med mere end to slags lægemidler/indholdsstoffer, skal du være opmærksom på, at du ikke kun får ét resultat, men et antal 1+1 kombinationer. Et eksempel: Hvis du søger på samtidig brug af en p-pille, et blodtrykssænkende lægemiddel og et sovemiddel, får du 3 mulige resultater:
A: kombinationen af p-pille og blodtrykssænkende lægemiddel
B: kombinationen af p-pille og sovemiddel
C: kombinationen af blodtrykssænkende lægemiddel og sovemiddel
Du får de parvise kombinationer, der er videnskabeligt undersøgt.
Nej, du skal ikke angive dosis (500mg paracetamol) eller interval (2xdaglig), når du skal søge på et præparat eller indholdsstof. Det er kun selve præparatnavnet eller navnet på indholdsstoffet, du skal skrive. Vælg eventuelt bare navnet fra listen.
Det er desværre sådan, at der indtil videre kun kan søges på indholdsstof, når det gælder naturlægemidler.
Dette sker, når du søger på et kombinationspræparat. Når du søger på et kombinationspræparat, får du præsenteret et resultat for hvert af disse indholdsstoffer.
Indholdet i databasen er resultatet af grundige vurderinger af videnskabelige artikler og konklusioner fra humane forsøg. Hvis du kun får én interaktion på trods af, at du har indtastet flere præparater eller indholdsstoffer, skyldes det, at der endnu ikke er beskrevet (eller fundet) interaktioner af de andre indholdsstoffer i den videnskabelige litteratur.
På Lægemiddelstyrelsens hjemmeside, og i månedsbladet Rationel Farmakoterapi, juni 2015.
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Lægemiddelstyrelsen
Axel Heides Gade 1
2300 København S
Tlf.nr 44 88 95 95
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Interaktionsoplysninger
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1. Indholdsstof sertralin |


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Interaktionsoplysninger for olanzapin og sertralin |
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En TDM-analyse finder ingen forskelle i olanzapin koncentration/dosis mellem kombinationsbehandlingen olanzapin og sertralin og monoterapi med olanzapin.
ingen
dokumenteret
antidepressiva, SSRI citalopram, escitalopram, fluoxetin, fluvoxamin, paroxetin, sertralin antipsykotika, atypiske amisulprid, aripiprazol, asenapin, brexpiprazol, clozapin, loxapin, lurasidon, olanzapin, paliperidon, quetiapin, risperidon, sertindol, sulpirid, ziprasidon
Kun et relativt begrænset antal af de mange mulige kombinationer af interaktioner mellem SSRI og antispykotika har været genstand for egentlige interaktionsstudier. Helt generelt bør der udvises forsigtighed ved samtidig behandling med fluoxetin/paroxetin og antipsykotika. Mange antipsykotika er substrater for bl. a. CYP2D6, som hæmmes i et klinisk relevant omfang af især fluoxetin men også paroxetin. Hvis kombinationer heraf vælges, tilrådes det at intensivere monitoreringen af plasmakoncentrationer af de involverede antipsykotika. Citalopram påvirker ikke plasmakoncentrationen af clozapin. Citalopram og escitalopram øger serumkoncentrationen af quetiapin med 16%. Paroxetin øger plasmakoncentrationen af risperidon med en faktor 2 og aripiprazol med faktor 1.5, mens der ikke er effekt på clozapin, og kun en mindre øgning af plasmakoncentrationen af paliperidon, som ikke er klinisk relevant. Sertralin påvirker ikke plasmakoncentrationen af clozapin i et klinisk relevant omfang. Fluvoxamin øger plasmakoncentrationen af clozapin med en faktor 2-5 og olanzapin med en faktor 2. Fluvoxamin doser over 200 mg dagligt kan muligvis øge risperidons plasmakoncentrationen med ca. 25%. Fluvoxamin hæmmer især CYP1A2, som medvirker ved metabolisering af Clozapin og Olanzapin. Endvidere bliver CYP3A4 også hæmmet af fluvoxamin, som quetiapin metaboliseres af. Fluoxetin øger plasmakoncentrationen af clozapin (58%), risperidon (75%) og quetiapin (26%). Aripiprazol-metabolismen hæmmes i mindre omfang af escitalopram. Der er i litteraturen ikke lokaliseret andre studier eller kasuistikker omhandlende interaktion mellem antidepressiva, SSRI og antipsykotika, atypiske.
Litteraturgennemgang - Vis
Aripiprazol og citalopram/escitalopram/fluoxetin/levomepromazin I et studie måles serumkoncentration af aripiprazol i monoterapi (23 patienter) og i samtidig administration med andre stoffer. Gennemsnitlig dosis af aripiprazol var 19,9 mg/dag. I 5 patienter, der samtidigt fik CYP2D6 hæmmere (3 på levomepromazin og 2 på fluoxetin) sås en gennemsnitlig stigning på 44% i koncentration/dosis ratio af aripiprazol, sammenlignet med patienter i monoterapi. Hos 6 patienter, der samtidig fik svage CYP2D6 hæmmere, citalopram eller escitalopram, sås en gennemsnitlig stigning på 39% i koncentration/dosis ratio af aripiprazol, sammenlignet med patienter i monoterapi, Castberg I og Spigset O, 2007.
Aripiprazol og escitalopram/sertralin/fluoxetin/paroxetin I et studie måles serumkoncentration af aripiprazol i monoterapi (79 prøver) og i samtidig administration med andre stoffer (282 prøver). Gennemsnitlig dosis af aripiprazol, fluoxetin, paroxetin og sertralin var 15 mg/dag. I patienter der samtidig administrerede CYP2D6 hæmmere (9 fluoxetin og 3 paroxetin prøver) sås en gennemsnitlig stigning på 45% i koncentration/dosis ratio af aripiprazol, sammenlignet med prøver fra patienter i monoterapi. Ved patienter der samtidig fik escitalopram (38 prøver) sås en gennemsnitlig stigning på omkring 20% i koncentration/dosis ratio af aripiprazol, sammenlignet med prøver fra patienter i monoterapi. Ved patienter der samtidig administrerede sertralin (14 prøver) sås ingen signifikant indflydelse på farmakokinetikken af aripiprazol,Waade RB, Christensen H et al, 2009. Boulton DW, Balch AH et al, 2010 rapporterer to studier: Et studie i raske frivillige, der blev behandlet med escitalopram (10 mg, n = 25) + placebo eller aripiprazol (10-20mg) i 14 dage samt et andet studie i patienter med depression, der havde responderet utilstrækkeligt på behandling med alene SSRI'er (escitalopram (10-20 mg), fluoxetin (20-40 mg), paroxetin (37,5-50 mg) eller sertralin (100-150 mg), og som efterfølgende fik tilføjet placebo (eller aripiprazol (2-20 mg) til behandlingsregimet. Resultaterne viste ingen ændring i plasmakoncentrationerne af nogle SSRIer ved samtidig behandling med aripiprazol hos hverken raske frivillige eller depressive patienter. Aripiprazol og escitalopram Et randomiseret farmakokinetisk forsøg med 13 japanske skizofrene patienter, viste ikke en signifikant ændring i plasmakoncentrationen af aripiprazol, ved samtidig administration af escitalopram, i et 95 % konfidensinterval. Patienterne havde alle modtaget behandling med aripiprazol i 2 uger, for at opnå en steady state plasmakoncentration. Herefter blev 10 mg escitalopram co-administreret 1 gang dagligt i 2 uger Nemoto K, Mihara K et al, 2014. Aripiprazol og paroxetin I et kontrolleret klinisk forsøg med 14 japanske skizofrene patienter, sås en signifikant dosisafhængig øgning af aripiprazols plasmakoncentration ved co-administration af paroxetin, Nemoto K, Mihara K et al, 2012. Patienterne havde været i behandling med aripiprazol i minimum 2 uger inden tillæg af paroxetin 10 mg/d i løbet af den første uge og derefter en dosisøgning til 20 mg/d den anden uge. Der sås ingen ekstrapyramidale bivirkninger. Mekanisme: Paroxetin hæmmer CYP2D6, som er vigtig i metaboliseringen af aripiprazol. Asenapin og fluvoxamin I et klinisk studie (ifølge produktresumeet for asenapin) resulterede coadministration af en enkelt dosis asenapin 5 mg og fluvoxamin 25 mg x 2 dgl. i en 29% forøgelse af asenapins AUC. Den fulde terapeutiske dosis fluvoxamin forventes at give en større forøgelse af plasmakoncentrationen for asenapin. Mekanisme: Fluvoxamin hæmmer CYP1A2 for hvilket asenapin er substrat, SPC for Sycrest, 2013. Asenapin og paroxetin
I et klinisk studie med 15 raske forsøgspersoner (ifølge produktresumeet for asenapin) resulterede samtidig indgift af en enkelt dosis paroxetin 20 mg (CYP2D6-substrat og hæmmer) og asenapin 5 mg x 2 dgl., i næsten en fordobling af paroxetin-eksponeringen. Mekanisme: Asenapin er en svag hæmmer af CYP2D6 og asenapin forstærker den hæmmende effekt af paroxetin på dets egen metabolisme, SPC for Sycrest, 2013. Clozapin og citalopram I et add-on studie af 5 patienter fandtes ingen påvirkning af plasmakoncentrationen af clozapin efter tillæg af citalopram, Taylor D, Ellison Z et al, 1998; Hiemke C, Weigmann H et al, 1994. Clozapin og fluoxetin I et add-on studie af 10 skizofrene patienter fandtes en stigning af clozapinkoncentrationen på 58% ( fra 348 til 550 ng/l) efter tillæg af 20 mg fluoxetin, Spina E, Avenoso A et al, 2001. I en enkelt case rapport fandtes derimod ingen stigning i clozapinkoncentrationen efter tillæg af 80 mg fluoxetin til behandlingen, Eggert AE, Crismon ML et al, 1994. Centorrino F, Baldessarini RJ et al, 1996 finder i en parallel undersøgelse mellem to grupper i henholdsvis monoterapi med clozapin og i kombinationsbehandling, at sidstnævnte gruppe har et signifikant højere serum clozapin end monoterapigruppen, henholdsvis 417 mod 345 ng/l. En 36-årig skizofren mand (Sandson NB, Cozza KL et al, 2007) fik bla. clozapin 200 mg bid. Behandling med fluoxetin blev tilføjet, og clozapin niveauet blev målt til 225 ng/ml. Dosis blev forøget til 600 mg/dg og clozapin blev nu målt til 1,339 ng/ml. På trods af det stærkt forøgede niveau oplevede patienten ingen bivirkninger. Derfor blev niveauet målt igen, og det lå stadig højt, 1,089 ng/ml. Formodet mekanisme: fluoxetin hæmmer CYP2D6, og i mindre grad CYP1A2, 2C9/19, 2D6 og 3A4. Alle enzymerne er involveret i metabolismen af clozapin, hvilket kan være forklaringen på det forøgede clozapin-niveau. Clozapin og fluvoxamin I et farmakokinetisk studie omhandlende 9 skizofrene patienter fandtes stigning i AUC og Cmax af clozapin med henholdsvis en faktor 3 og en faktor 1,5 efter tillæg af fluvoxamin, Chang WH, Augustin B et al, 1999. I et add-on studie omhandlende 16 skizofrene patienter fandtes en dosis afhængig stigning i plasmakoncentrationen af clozapin på en faktor 3,5 til 5 efter tillæg af henholdsvis 50 og 100 mg fluvoxamin, Fabrazzo M, La Pia S et al, 2000. I et add-on studie af 16 skizofrene patienter fandtes en stigning i plasmakoncentrationen af clozapin med en faktor 3 efter tillæg af fluvoxamin, Wetzel H, Anghelescu I et al, 1998. Et prospektivt studie (Wang CY, Zhang ZJ et al, 2004) viser, at ved samtidig indgift af en enkeltdosis clozapin og flerdosis fluvoxamin hos 9 raske forsøgspersoner observeres en stigning i Cmax for clozapin på 14% (fra 22,4 til 25,4 ng/ml), stigning i AUC(0-8) på 42% fra 307,8 til 434,5 ng/timer/ml), fald i den orale clearance på 78% (fra 5,9 til 1,3 liter/time, fald i Vd på 38% (fra 6,9 til 4,3 liter) og forlængelse af halveringstiden på 374% (fra 27,7 til 131,3 timer). I et prospektivt studie med 16 skizofrene patienter i stabil clozapin-behandling gives 50 mg fluvoxamin som tillægsbehandling i minimum 14 dage. Serumkoncentration af clozapin og clozapin-metabolitter stiger gennemsnitligt med en faktor 2-3 og op til en faktor 5, Szegedi A, Anghelescu I et al, 1999. Fem kasuistikker omhandler ialt 9 patienter (DuMortier G, Lochu A et al, 1996; Hiemke C, Weigmann H et al, 1994; Dequardo JR og Roberts M, 1996; Heeringa M, Beurskens R et al, 1999; Koponen HJ, Leinonen E et al, 1996), hvor der observeres stigninger i serumkoncentrationen af clozapin som følge af kombinationsbehandling med fluvoxamin. En sjette kasuistik beskriver en patient med paranoid skizofreni, som er i behandling med 900 mg clozapin pr. dag, Vaios P, Sofia T et al, 2005. 6 dage efter tillægsbehandling med 100 mg fluvoxamin pr. dag indlægges patienten på hospitalet med dystoni, dysartri, dysphagi, hypersalivation, svimmelhed og et EKG, som viser abnormaliteter. En uge efter ophør af fluvoxamin og reduktion af clozapin-dosis til 700 mg/dag forsvinder bivirkningerne, EKG-abnormaliteterne aftager og forsvinder helt efter 1 måned. Endnu en kasuistik (Chong SA, Tan CH et al, 1997) beretter om en patient med skizofreni, som efter seponering af uvirksom behandling opstartes i behandling med clozapin (500 mg dgl.). Herefter opnår patienten bedring i de psykotiske symptomer (Brief Psychiatric Rating Scale (BPRS) falder fra 45 til 34), men senere ses forværring (BPRS stiger til 40). Øget clozapin-dosis giver ingen bedring. Clozapin-koncentrationen er 1146 ng/ml. Derefter tillægges behandling med fluvoxamin med 50 mg dgl., hvilket dog medfører en forværring af de psykotiske symptomer (BPRS stiger til 64). Clozapin-koncentrationen stiger efter 8 dage til 2410 ng/ml og til 2750 ng/ml efter 28 dage. Kuo FJ, Lane HY et al, 1998 beretter om 2 patienter: En patient med paranoid skizofreni starter clozapin-behandling (titrering til 400 mg dgl., clozapin-koncentration 686 ng/mL). Idet der ikke opnås tilstrækkelig klinisk effekt, tillægges fluvoxamin (25 mg dgl.) til behandlingen. Efter 4 dage oplever patienten ekstrapyramidale symptomer (Extrapyramidal Symptom Rating Scale (ESRS) = 6 sammenlignet med ESRS = 0 før tillægsbehandling), som forværres efter 3 uger (ESRS = 8). Clozapinkoncentrationen er under kombinationsbehandlingen 818 ng/ml. En anden patient er i behandling med clozapin (600 mg dgl., clozapinkoncentration 1.293 ng/ml), men på grund af manglende effekt forsøges tillægsbehandling med fluvoxamin (25 mg dgl.). 6 dage senere oplever patienten ekstrapyramidale symptomer (ESRS = 7 sammenlignet med ESRS = 0 før tillægsbehandling), som forværres (ESRS = 9). Clozapinkoncentrationen stiger under kombinationsbehandlingen til 1,549 ng/ml. En kasuistik (Ozdemir V, Kalow W et al, 2001) beskriver en behandlingsresistent skizofren patient med BPRS=71 på højdosis clozapin (750 mg tre gange om dagen p.o.), hvor der samtidig måles en lav plasmakoncentration af både clozapin (482 nmol/L) og norclozapin (446 nmol/L). I første omgang tillægges fluvoxamin (25 mg/d), og der ses en øgning af clozapin serumkoncentration (1053 nmol/L), men ingen forbedring af psykose (BPRS=70). Ved øgning af fluvoxamin til 50 mg/d stiger clozapin serumkoncentration til over minimum terapeutisk koncentration (1150 nmol/L) og der observeres en klinisk forbedring af psykosen (BPRS=37). Virkningsmekanisme: Mekanismen formodes at være fluvoxamins øgning af plasmakoncentration af clozapin. Dette skyldes ifølge Vaios P, Sofia T et al, 2005 og Ozdemir V, Kalow W et al, 2001, at fluvoxamin hæmmer CYP1A2, og ifølge Olesen OV og Linnet K, 2000, at fluvoxamin hæmmer clozapins N-demethylering overvejende via CYP1A2 og CYP2C19. Clozapin og paroxetin I et add-on studie af 14 skizofrene patienter fandtes ingen effekt på plasmakoncentrationen af clozapin efter tillæg af paroxetin, Wetzel H, Anghelescu I et al, 1998. I modsætning hertil fandtes i et add-on studie af 9 skizofrene patienter en stigning i plasmakoncentrationen af clozapin med 31%, Spina E, Avenoso A et al, 2000. Centorrino F, Baldessarini RJ et al, 1996 finder i en parallel undersøgelse mellem to grupper i henholdsvis monoterapi med clozapin og i kombinationsbehandling med paroxetin, at sidstnævnte gruppe har et signifikant højere serum clozapin end monoterapigruppen. Clozapin og sertralin I et add-on studie af 8 skizofrene patienter fandtes ingen effekt på plasmakoncentrationen af clozapin efter tillæg af sertralin, Spina E, Avenoso A et al, 2000. I studiet af Centorrino F, Baldessarini RJ et al, 1996 på 10 ambulante skizofrene patienter i behandling med 92,5 mg sertralin og 279 mg clozapin dagligt fandtes serum clozapin til 345ng/l i forhold til 265ng/l i en kontrolgruppe bestående af 40 patienter i monoterapi. En case report (Chong SA, Tan CH et al, 1997) beretter om en patient med paranoid skizofreni, som behandles med 175 mg clozapin dagligt. Derudover behandles patienten med 10 mg propranolol dagligt samt 2 mg trihexyphenidyl dagligt. 50 mg sertralin dagligt tillægges behandlingen, hvorefter patientens psykose forværres ligesom obsessiv-kompulsive symptomer forværres. Clozapin-koncentrationen stiger fra 325 ng/ml før sertralin-behandling til 695 ng/ml. Behandling med sertralin ophører og 2 uger senere er clozapin-koncentrationen 460 ng/ml. Olanzapin og fluoxetin Gossen D, de Suray JM et al, 2002 viser på 15 raske forsøgspersoner, at AUC for enkeltdosis olanzapin steg fra 272 til 321 ng/time/ml efter samtidig indgift af 60 mg fluoxetin. Efter 8 dages behandling med fluoxetin daglig fandtes AUC for olanzepin til 314ng/time/ml. Hos en patient (Reeves RR og Ladner ME, 2005) i behandling med olanzapin og fluoxetin rapporteres om bivirkninger i form af mani. Hvorvidt bivirkninger skyldes kombinationen olanzapin og fluoxetin er uvist. Olanzapin og fluvoxamin I et add-on studie af 8 skizofrene patienter resulterede en samtidig administration af fluvoxamin i øgning af olanzapins Cmin med knapt 100%. Der observeredes ikke bivirkninger i forbindelse hermed, Hiemke C, Peled A et al, 2002. Ved samtidig indgift af en enkeltdosis olanzapin og flerdosis fluvoxamin hos raske forsøgspersoner (Chiu CC, Lane HY et al, 2004; Wang CY, Zhang ZJ et al, 2004) observeres en stigning i Cmax for olanzapin på 50-55% (fra 19,5 til 29,1 n/ml), stigning i AUC(0-8) på 30-76% (fra 728,5 til 1279,5 ng/timer/ml) og et fald i den orale clearance på 42% (fra 14,6 til 8,5 l/time). I samme studie (Wang CY, Zhang ZJ et al, 2004) observeres et fald i Vd på 32% (fra 435,5 til 299,2 liter), nedsættelse af tmax med 32% (fra 3,8 til 2,6 timer) og en forlængelse af t1/2 med 44% (fra 32,2 til 46,1 timer). Et studie har fundet, at koncentration/dosis-ratio for olanzapin hos patienter i behandling med såvel fluvoxamin som olanzapin (n = 10) var øget med en faktor 2,3 i forhold til patienter alene i behandling med olanzapin (n = 134). Mekanisme: hæmning af olanzapins omsætning i CYP1A2, Weigmann H, Gerek S et al, 2001. Albers LJ, Ozdemir V et al, 2005 angiver, at der ved samtidig behandling med fluvoxamin og olanzapin bør ske en dosisjustering af olanzapin med ca. 25%, for at fastholde serumkoncentrationen af olanzapin i terapeutisk niveau.
Olanzapin og sertralin Et studie har fundet, at koncentration/dosis ratio for olanzapin hos patienter i kombinationsbehandling med sertralin og olanzapin (n = 21) ikke var forskellig fra patienter i behandling med olanzapin alene (n = 134), Weigmann H, Gerek S et al, 2001.
Paroxetin og paliperidon I et farmakokinetisk, single-center, randomiseret, open-label, single-dose, crossover studie med 60 raske mænd i kombinationsbehandling med 20 mg paroxetin og 3 mg paliperidon, blev der fundet en mindre øgning i Cmax og AUC og et mindre fald i clearance for paliperidon. Dette anses dog ikke for at være klinisk relevant, på trods af at paroxetin er en potent og selektiv inhibitor af CYP2D6. Berwaerts J, Cleton A et al, 2009. Quetiapin og citalopram/escitalopram I et retrospektivt studie (Castberg I, Skogvoll E et al, 2007b) blev serumkoncentrationen af quetiapin målt hos 1179 patienter, og mulig farmakokinetisk interaktion med i alt 41 co-administrerede lægemidler blev undersøgt. Det blev fundet, at bl.a. citalopram/escitalopram øgede dosiskorrigeret serumkoncentration af quetiapin med 16%.
Quetiapin og fluoxetin Et farmakokinetisk studie med 13 skizofrene patienter i kombinationsbehandling med 300 mg quetiapin og 60 mg fluoxetin dagligt, fandt en øgning af AUC for quetiapin med 12%, samt en øgning af Cmax for quetiapin med 26% ved kombinationsbehanling. Oral clearence for quetiapin faldt signifikant med 11%, dog uden klinisk signifikans. Der var ingen effekt på bivirkningsfrekvens eller alvorlighed i en side effect rating scale Potkin SG, Thyrum PT et al, 2002a. I et retrospektivt studie (Castberg I, Skogvoll E et al, 2007b) blev serumkoncentrationen af quetiapin målt hos 1179 patienter, og mulig farmakokinetisk interaktion med i alt 41 co-administrerede lægemidler blev undersøgt. For fluoxetin fandt studiet ingen statistisk signifikant effekt på dosiskorrigeret serumkoncentration af quetiapin.
Quetiapin og fluvoxamin Hos en patient (Matsumoto R, Kitabayashi Y et al, 2005) rapporteres om forekomst af neuroleptisk, malignt syndrom ved kombinationsbehandling med quetiapin og fluvoxamin. I et retrospektivt studie (Castberg I, Skogvoll E et al, 2007b) blev serumkoncentrationen af quetiapin målt hos 1179 patienter, og mulig farmakokinetisk interaktion med i alt 41 co-administrerede lægemidler blev undersøgt. Det blev fundet, at fluvoxamin øgede dosiskorrigeret serumkoncentration af quetiapin med 159%. Mekanisme: Hæmning af CYP3A4.
Quetiapin og paroxetin/sertralin I et retrospektivt studie (Castberg I, Skogvoll E et al, 2007b) blev serumkoncentrationen af quetiapin målt hos 1179 patienter, og mulig farmakokinetisk interaktion med i alt 41 co-administrerede lægemidler blev undersøgt. For paroxetin og sertralin fandt studiet ingen statistisk signifikant effekt på dosiskorrigeret serumkoncentration af quetiapin.
Risperidon og citalopram Hos en patient i behandling med citalopram og risperidon (Blaschke D, Parwani AS et al, 2007) er rapporteret torsade de pointes. Det er uafklaret, hvorvidt torsdade de pointes skyldes interaktion eller additive effekter.
Risperidon og fluoxetin I et åbent add-on studie blandt 11 patienter resulterede en samtidig administration af 20 mg fluoxetin med 4 mg risperidon i en stigning af AUC for risperidon og den aktive metabolit 9-hydroxyrisperidon med 40 %. Denne stigning sås dog kun blandt 8 CYP2D6 EM'er, der ikke var statistisk signifikant effekt blandt 3 PM'er, Bondolfi G, Eap CB et al, 2002. Der observeredes ingen ændringer i bivirkningsprofilen blandt patienterne. I et åbent add-on studie af 10 patienter resulterede tillæg af 20 mg fluoxetin dagligt til en bestående risperidonbehandling i en øgning af den samlede koncentration af risperidon og 9-hydroxyrisperidon med 75%. En patient eksluderedes på grund af meget høje koncentration og udvikling af akatisi, medens to andre patienter udviklede parkinsonsymptomer, Spina E, Avenoso A et al, 2002. Risperidon og fluvoxamin Hos 11 skizofrene patienter i behandling med 3-6 mg risperidon dagligt (D'Arrigo C, Migliardi G et al, 2005) observeres efter tillæg af 100 mg fluvoxamin dagligt i 4 uger til behandlingen ingen statistisk signifikante ændringer i plasmakoncentrationen for risperidon. Efter øgning af fluvoxamin dosis til 200 mg dagligt observeres en 26% stigning i plasmakoncentrationen af risperidon hos fem af patienterne.
Risperidon og paroxetin I et åbent add-on studie af 10 patienter resulterede tillæg af paroxetin til en bestående risperidonbehandling, i en øgning af summen af risperidon og 9-hydroxyrisperidon med 45%. En patient udviklede parkinsonsymptomer, Spina E, Avenoso A et al, 2001. Hos en patient (Barnhill J, Susce MT et al, 2005) i behandling med paroxetin og risperidon observeres en forlænget halveringstid for isomeren R-risperidon. Ved samtidig indgift af paroxetin (10-40 mg/daglig) til 12 skitzofrene patienter i behandling med risperidon (Saito M, Yasui FN et al, 2005) observeres en stigning i risperidon plasmakoncentrationen varierende fra en faktor 4-10. Hos en patient (Al-Chekakie MO, Ketz JM et al, 2006) i behandling med risperidon og paroxetin rapporteres om hypothermia, dvs. fald i patientens kropstemperatur. Fald i kropstemperatur er en kendt bivirkning ved risperidon og er formentlig blevet forstærket af interaktionen med paroxetin. Sertindol og fluoxetin/paroxetin Visse SSRI’ere, såsom fluoxetin og paroxetin (potente CYP2D6 hæmmere), kan øge plasmaniveauet af sertindol med en faktor 2-3. Sertindol bør derfor anvendes med stor forsigtighed sammen med disse lægemidler og kun i de tilfælde, hvor den forventede fordel ved behandlingen er større end den mulige risiko. Det kan være nødvendigt med en lavere vedligeholdelsesdosis af sertindol, og der bør foretages omhyggelig EKG monitorering både før og efter dosisjustering af disse lægemidler. SmPC for Serdolect, 2014
Vaios P;Sofia T;Dimitrios P;Venetsanos M, Schizophr Res , 2005, 79(2-3): 345-346-3; Acute effects of clozapine-fluvoxamine combination [2] Szegedi A;Anghelescu I;Wiesner J;Schlegel S;Weigmann H;Hartter S;Hiemke C;Wetzel H, Pharmacopsychiatry, 1999, 32:148-153; Addition of low-dose fluvoxamine to low-dose clozapine monotherapy in schizophrenia: drug monitoring and tolerability data from a prospective clinical trial Combining fluvoxamine and clozapine may be a strategy to improve therapeutic effects on negative symptoms in schizophrenic patients. Fluvoxamine, however, markedly inhibits the metabolism of clozapine, and hazardous side effects may result. This study prospectively investigated the safety and tolerability of an add-on therapy with fluvoxamine to a clozapine monotherapy in schizophrenic patients. Sixteen schizophrenic patients received 50 mg fluvoxamine as a comedication after having reached steady-state conditions under clozapine monotherapy. Patients were monitored for subjective adverse events, laboratory parameters, EEG and ECG recordings, orthostatic hypotension and their psychopathology. Concomitantly, serum concentrations of clozapine and metabolites were measured during monotherapy and after addition of fluvoxamine. In all patients, the serum concentrations of clozapine and metabolites were markedly increased (average: 2-3 fold, up to 5 fold for clozapine) after addition of fluvoxamine. Side effects remained almost unchanged in frequency and severity in spite of the pharmacokinetic interactions. ECG or laboratory parameters and orthostatic tests were similar under monotherapy and comedication. Minimal increases of EEG abnormalities were observed, but they were not associated with clinical impairment. Epileptic activities were always absent. The psychopathology improved which continued after start of the comedication. Though the addition of fluvoxamine to clozapine medication was well tolerated and critical side effects were absent, the combined treatment should be controlled by drug monitoring, as serum concentrations of clozapine increased to unpredictably high levels. Further studies have to find out if the combined treatment could be advantageous to clozapine monotherapy  Sandson NB;Cozza KL;Armstrong SC;Eckermann G;Fischer BA;Phillips B, Psychosomatics, 2007, 48:170-175; Clozapine case series Clozapine is not a drug that is ever used casually. Patients generally are afflicted with severe illnesses and have demonstrated treatment resistance and/or intolerance to other therapeutic options before clozapine is seriously considered. When the clinical stakes are this high, it is especially important that physicians gain an appreciation for the various drug-drug interactions that can significantly increase or decrease clozapine blood levels; such pharmacokinetic changes can derail clozapine treatment by producing clozapine toxicity or loss of antipsychotic efficacy, respectively. The authors present a case series of five drug-drug interactions involving clozapine, each of which illustrates different mechanisms by which the metabolism of clozapine can be altered. Exploring these cases should help clinicians anticipate and avoid these undesirable drug-drug interactions  Taylor D;Ellison Z;Ementon SL;Wickham H;Murray R, Int Clin Psychopharmacol, 1998, 13:19-21; Co-administration of citalopram and clozapine: effect on plasma clozapine levels Antidepressants are frequently used in the treatment of depressive symptoms associated with schizophrenia. In patients taking clozapine, choice of antidepressant is complicated by additive pharmacodynamic effects and by pharmacokinetic interactions. We predicted that citalopram would not elevate plasma clozapine levels when the two drugs were co-administered because it does not inhibit the relevant enzyme systems. In this preliminary study of five patients given citalopram and clozapine there was no overall change in mean clozapine levels. Based on this limited evidence, citalopram might be the antidepressant of choice in patients taking clozapine Reeves RR;Ladner ME, South Med J, 2005, 98:1152-1153; Does olanzapine-fluoxetine combination increase the risk of mania in poorly compliant bipolar depressed patients? Chiu CC;Lane HY;Huang MC;Liu HC;Jann MW;Hon YY;Chang WH;Lu ML, J Clin Pharmacol, 2004, 44:1385-1390; Dose-dependent alternations in the pharmacokinetics of olanzapine during coadministration of fluvoxamine in patients with schizophrenia Olanzapine, an atypical antipsychotic agent, is a substrate of the cytochrome P4501A2 (CYP1A2) enzyme. Administration of a potent CYP1A2 inhibitor (eg, fluvoxamine) may alter the pharmacokinetics of olanzapine. This study investigated the pharmacokinetic interactions between olanzapine and fluvoxamine in patients with schizophrenia. Ten male smokers were administrated a single dose of olanzapine 10 mg at baseline, followed by 2 weeks of fluvoxamine 50 mg/day and another 2 weeks of fluvoxamine 100 mg/day. Olanzapine 10 mg was given at day 10 during each fluvoxamine treatment. After pretreatment with fluvoxamine, the area under the curve, maximal plasma concentration, and half-time of olanzapine were significantly increased by 30% to 55%, 12% to 64%, and 25% to 32%, respectively. Volume of distribution and apparent clearance were significantly reduced by 4% to 26% and 26% t O 38%, respectively, after administration of fluvoxamine. Increases in area under the plasma concentration-time curve from time 0 to infinity appear to be dose dependent. Presumably, altered olanzapine pharmacokinetics are attributed to the inhibition of CYP1A2. Patients treated with the combination of olanzapine and fluvoxamine should be monitored carefully  Saito M;Yasui FN;Nakagami T;Furukori H;Kaneko S, J Clin Psychopharmacol, 2005, 25(6): 527-532-532; Dose-dependent interaction of paroxetine with risperidone in schizophrenic patients Augmentation with paroxetine (10-40 mg/d) for antipsychotic treatment may improve the negative symptoms in schizophrenic patients but involves a risk of drug-drug interaction. We studied the effects of paroxetine on plasma concentrations of risperidone and 9-hydroxyrisperidone and their clinical symptoms in risperidone-treated patients. Twelve schizophrenic inpatients with prevailingly negative symptoms receiving risperidone 4 mg/d were, in addition, treated with incremental doses of paroxetine for 12 weeks (10, 20, and 40 mg/d for 4 weeks each). Plasma concentrations of risperidone and 9-hydroxyrisperidone were quantified with liquid chromatography-mass spectrometry mass-mass spectrometry together with clinical assessments before and after each phase of the 3 paroxetine doses. Risperidone concentrations during coadministration of paroxetine 10, 20, and 40 mg/d were 3.8-fold (95% confidence interval, 3.2-5.8, P < 0.01), 7.1-fold (95% confidence interval, 5.3-16.5, P < 0.01), and 9.7-fold (95% confidence interval, 7.8-22.5, P < 0.01) higher than that before paroxetine coadministration, respectively. Active moiety (risperidone plus 9-hydroxyrisperidone) concentration was not increased during the paroxetine 10 mg/d (1.3-fold, not significant) or 20 mg/d (1.6-fold, not significant), but were significantly increased by 1.8-fold (95% confidence interval, 1.4-2.7, P < 0.05) during the paroxetine 40 mg/d. Significant improvement in negative symptoms was observed from 10 to 40 mg/d of paroxetine, whereas scores in extrapyramidal side effects during 20 and 40 mg/d of paroxetine were significantly higher than baseline score. This study indicates that paroxetine increases plasma risperidone concentration and active moiety concentration in a dose-dependent manner. Low-dose coadministration of paroxetine with risperidone may be safe and effective in the treatment of schizophrenic patients with negative symptoms. Copyright < copyright > 2005 by Lippincott Williams & Wilkins  Potkin SG;Thyrum PT;Alva G;Carreon D;Yeh C;Kalali A;Arvanitis LA, J Clin Psychopharmacol, 2002, a, 22:174-182; Effect of fluoxetine and imipramine on the pharmacokinetics and tolerability of the antipsychotic quetiapine The effects of fluoxetine and imipramine on the pharmacokinetics and nonpsychiatric side effect profile of quetiapine fumarate were investigated in 26 patients with schizophrenia, schizoaffective disorder, or bipolar disorder in a multicenter, two-period, multiple-dose, open-label, randomized trial. Over a 1- to 2-week period, patients were titrated to a 300-mg twice-daily dose of quetiapine. Patients treated for at least 7 days at the target dose entered a combination therapy period, receiving fluoxetine (60 mg daily) or imipramine (75 mg twice daily) for 8 days. Key assessments included pharmacokinetic analysis of quetiapine, the Udvalg for kliniske undersogelser (UKU) Side Effect Rating Scale, and safety evaluations (e.g., adverse events, electrocardiograms, laboratory tests, and vital signs). Fluoxetine increased the quetiapine area under the plasma concentration time curve during a 12-hour interval (+12%), maximum plasma concentration during the dosing interval (C(ss)(max); +26%), and minimum plasma concentration at the end of the dosing interval (+8%), although it decreased oral clearance (-11%). The change in C(ss)(max) was statistically although not clinically significant. Imipramine did not affect the pharmacokinetics of quetiapine. Overall, scores on the UKU Side Effect Rating Scale improved during combination therapy with either agent, and no statistically significant deterioration was observed for any item. For safety assessments, the only clinically remarkable event was an imipramine-associated complete left bundle branch block in one patient. No unexpected side effects were reported. In conclusion, combination therapy with quetiapine and fluoxetine or imipramine had a minimal effect on quetiapine pharmacokinetics and was well tolerated  Spina E;Avenoso A;Facciola G;Fabrazzo M;Monteleone P;Maj M;Perucca E;Caputi AP, Int Clin Psychopharmacol, 1998, 13:141-145; Effect of fluoxetine on the plasma concentrations of clozapine and its major metabolites in patients with schizophrenia The effect of fluoxetine on the plasma concentrations of clozapine and its major metabolites was studied in 10 schizophrenic patients with residual negative symptoms. Patients stabilized on clozapine therapy (200-450 mg/day) received additional fluoxetine (20 mg/day) for eight consecutive weeks. During fluoxetine administration, mean plasma concentrations of clozapine, norclozapine and clozapine N-oxide increased significantly by 58%, 36% and 38%, respectively. There was no difference in negative symptomatology, as measured by the Scale for Assessment of Negative Symptoms, and the drug combination was generally well tolerated. The concomitant elevation in plasma levels of clozapine and its major metabolites suggests that fluoxetine inhibits the metabolism of clozapine by affecting pathways other than N-demethylation and N-oxidation. Close monitoring of clinical response and, possibly, plasma clozapine levels is recommended whenever fluoxetine is given to patients stabilized on clozapine therapy  D'Arrigo C;Migliardi G;Santoro V;Morgante L;Muscatello MR;Ancione M;Spina E, Pharmacol Res, 2005, 52(6): 497-501-501; Effect of fluvoxamine on plasma risperidone concentrations in patients with schizophrenia The effect of fluvoxamine on plasma concentrations of risperidone and its active metabolite 9-hydroxyrisperidone (9-OH-risperidone) was investigated in 11 schizophrenic patients with prevailingly negative or depressive symptoms. Additional fluvoxamine, at the dose of 100 mg/day, was administered for 4 weeks to patients stabilized on risperidone (3-6 mg/day). Mean plasma concentrations of risperidone, 9-OH-risperidone and the active moiety (sum of the concentrations of risperidone and 9-OH-risperidone) were not significantly modified following co-administration with fluvoxamine. After 4 weeks, fluvoxamine dosage was increased to 200 mg/day in five patients and then maintained until the end of week 8. At final evaluation, mean plasma levels of risperidone active moiety were not modified in the six patients who were still receiving the initial fluvoxamine dose, while concentrations increased slightly but significantly (by a mean 26% over pretreatment; P < 0.05) in the subgroup of five subjects treated with a final dose of 200 mg/day. Fluvoxamine co-administration with risperidone was well tolerated and no patient developed extrapyramidal side effects. These findings indicate that fluvoxamine at dosages up to 100 mg/day is not associated with clinically significant changes in plasma risperidone concentrations. However, higher doses of fluvoxamine may elevate plasma risperidone levels, presumably as a result of a dose-dependent inhibitory effect of fluvoxamine on CYP2D6-and/or CYP3A4-mediated 9-hydroxylation of risperidone. < copyright > 2005 Elsevier Ltd. All rights reserved  Castberg I;Spigset O, Pharmacopsychiatry, 2007, 40:107-110; Effects of comedication on the serum levels of aripiprazole: evidence from a routine therapeutic drug monitoring service INTRODUCTION: The objective of the study was to compare the serum concentrations of the atypical antipsychotic aripiprazole in monotherapy with the concentrations found during concomitant therapy with other drugs. METHODS: Samples analyzed for aripiprazole by a liquid chromatography-mass spectrometry method in a routine therapeutic drug monitoring setting were collected consecutively. RESULTS: Samples from 81 patients were included in the study. Comedication with the CYP3A4 inducer carbamazepine lowered the dose-adjusted aripiprazole concentration by 88%. Comedication with CYP2D6 inhibitors gave a mean concentration 44% higher than in the monotherapy group. Subjects comedicated with valproate had lower aripiprazole concentrations, while subjects comedicated with lamotrigine, citalopram/escitalopram and lithium had higher concentrations than the subjects in the monotherapy group. CONCLUSION: Although the study is small and the results should be interpreted very cautiously, it indicates that comedication with drugs inhibiting or inducing CYP2D6 or CYP3A4 affects the serum concentrations of aripiprazole. The other findings should be considered as preliminary and have to be replicated in a larger setting before firm conclusions can be drawn  Nemoto K;Mihara K;Nakamura A;Nagai G;Kagawa S;Suzuki T;Kondo T, Pharmacopsychiatry, 2014, 47:May; Effects of escitalopram on plasma concentrations of aripiprazole and its active metabolite, dehydroaripiprazole, in Japanese patients Introduction: The effects of escitalopram (10mg/d) coadministration on plasma concentrations of aripiprazole and its active metabolite, dehydroaripiprazole, were studied in 13 Japanese psychiatric patients and compared with those of paroxetine (10mg/d) coadministration. Methods: The patients had received 6-24mg/d of aripiprazole for at least 2 weeks. Patients were randomly allocated to one of 2 treatment sequences: paroxetine-escitalopram (n=6) or escitalopram-paroxetine (n=7). Each sequence consisted of two 2-week phases. Plasma concentrations of aripiprazole and dehydroaripiprazole were measured using liquid chromatography with mass spectrometric detection. Results: Plasma concentrations of aripiprazole and the sum of aripiprazole and dehydroaripiprazole during paroxetine coadministration were 1.7-fold (95% confidence intervals [CI], 1.3-2.1, p<0.001) and 1.5-fold (95% CI 1.2-1.9, p<0.01) higher than those values before the coadministration. These values were not influenced by escitalopram coadministration (1.3-fold, 95% CI 1.1-1.5 and 1.3-fold, 95% CI 1.0-1.5). Plasma dehydroaripiprazole concentrations remained constant during the study. Conclusion: The present study suggests that low doses of escitalopram can be safely coadministered with aripiprazole, at least from a pharmacokinetic point of view. Georg Thieme Verlag KG Stuttgart, New York  Nemoto K;Mihara K;Nakamura A;Nagai G;Kagawa S;Suzuki T;Kondo T, Ther Drug Monit, 2012, 34:188-192; Effects of paroxetine on plasma concentrations of aripiprazole and its active metabolite, dehydroaripiprazole, in Japanese patients with schizophrenia BACKGROUND: The effects of paroxetine coadministration on plasma concentrations of aripiprazole and its active metabolite, dehydroaripiprazole, were studied in 14 Japanese patients with schizophrenia. METHODS: The patients had been treated with aripiprazole (24 mg/d in 5 cases, 12 mg/d in 5 cases, and 6 mg/d in 4 cases) for at least 2 weeks. Paroxetine 10 mg/d was coadministered during the first week, and the dose was increased to 20 mg/d during the second week. Blood samples were taken 3 times, before the start of paroxetine and then 1 and 2 weeks after paroxetine coadministration. On the same days, the severity of illness and extrapyramidal adverse effects were evaluated by the clinical global impressions and the Drug-Induced Extra-Pyramidal Symptoms Scale, respectively. Plasma concentrations of aripiprazole and dehydroaripiprazole were measured using liquid chromatography with mass spectrometric detection. RESULTS: Plasma concentrations of aripiprazole and the sum of aripiprazole and dehydroaripiprazole during coadministration of paroxetine 10 and 20 mg/d were significantly (P < 0.05) higher (1.5-fold and 1.7-fold; 1.4-fold and 1.5-fold) than those before paroxetine coadministration. Those values during coadministration of paroxetine 20 mg/d were also significantly (P < 0.05) higher (1.1-fold and 1.1-fold) than those during coadministration of paroxetine 10 mg/d. Plasma concentrations of dehydroaripiprazole were unchanged throughout the study period. The mean clinical global impression score was significantly (P < 0.05) higher during the paroxetine 10 mg/d than that before coadministration, whereas the Drug-Induced Extra-Pyramidal Symptoms Scale scores remained unchanged during the study. CONCLUSIONS: This study suggests that lower doses (10-20 mg/d) of paroxetine coadministration increase plasma concentrations of aripiprazole and the sum of aripiprazole and dehydroaripiprazole  Dequardo JR;Roberts M, Am J Psychiatry, 1996, 153:840-841; Elevated clozapine levels after fluvoxamine initiation DuMortier G;Lochu A;Colen dM;Ghribi O;Roche-Rabreau D;DeGrassat K;Desce JM, Am J Psychiatry, 1996, 153:738-739; Elevated clozapine plasma concentrations after fluvoxamine initiation Hiemke C;Weigmann H;Hartter S;Dahmen N;Wetzel H;Muller H, J Clin Psychopharmacol, 1994, 14:279-281; Elevated levels of clozapine in serum after addition of fluvoxamine Heeringa M;Beurskens R;Schouten W;Verduijn MM, Pharm World Sci, 1999, 21:243-244; Elevated plasma levels of clozapine after concomitant use of fluvoxamine Selective serotonin reuptake inhibitors can be added to clozapine therapy in order to treat remaining negative symptoms and obsessive compulsive symptoms. The present case report describes a 44-year-old man exhibiting extremely elevated plasma levels of clozapine after the addition of fluvoxamine, up to 4160 mcg/l. The elevated plasma levels of clozapine, which were discovered 6 months after the SSRI was added, is likely to be caused by a drug-drug interaction. Clozapine is a substrate of CYP 1A2 and is predominantly metabolised in the liver. Of the SSRIs, fluvoxamine is one of the most potent inhibitors of the isoenzyme CYP 1A2. This case serves to emphasise the need for continuous attention to drug-drug interactions, especially when they might be easily overlooked due to the lack of clear symptoms Kuo FJ;Lane HY;Chang WH, J Clin Psychopharmacol, 1998, 18:483-484; Extrapyramidal symptoms after addition of fluvoxamine to clozapine Hiemke C;Peled A;Jabarin M;Hadjez J;Weigmann H;Hartter S;Modai I;Ritsner M;Silver H, J Clin Psychopharmacol, 2002, 22:502-506; Fluvoxamine augmentation of olanzapine in chronic schizophrenia: pharmacokinetic interactions and clinical effects Olanzapine is a substrate of the cytochrome P450 enzyme (CYP) 1A2. In this study, pharmacokinetic interactions and clinical effects of adding the CYP1A2 inhibitor fluvoxamine to steady-state olanzapine was examined in patients suffering from schizophrenia. Eight patients had been treated for at least 3 months with 10 to 20 mg/day olanzapine. Fluvoxamine (100 mg/day) was added (week 0) to the olanzapine treatment and continued for 8 weeks. Concentrations of olanzapine and its metabolite N-desmethylolanzapine and of fluvoxamine were analyzed at weeks 0, 1, 4, and 8. Addition of fluvoxamine resulted in a 12% to 112% ( < 0.01) increase of olanzapine from 31 +/- SD 15 ng/mL (week 0) to 56 +/- 31 ng/mL (week 8) in all patients. N-desmethylolanzapine concentrations were not significantly changed ( > 0.05). Fluvoxamine concentrations were 48 +/- 26 ng/mL on week 1 and 83 +/- 47 ng/mL on week 8. It is concluded that fluvoxamine affects olanzapine degradation and thus increases olanzapine concentrations. Although the combination was well tolerated in this sample and the negative symptom response appeared to be favorable in at least five patients, the combination therapy of olanzapine and fluvoxamine should be used cautiously and should be controlled by therapeutic drug monitoring to avoid olanzapine-induced side effects or intoxications  Weigmann H;Gerek S;Zeisig A;Muller M;Hartter S;Hiemke C, Ther Drug Monit, 2001, 23:410-413; Fluvoxamine but not sertraline inhibits the metabolism of olanzapine: evidence from a therapeutic drug monitoring service Therapeutic drug monitoring data of the new atypical neuroleptic drug olanzapine were used to study interactions with the selective serotonin reuptake inhibitors fluvoxamine and sertraline. The distribution of the ratio of concentration/daily dose (C/D; ng/mL per mg/d) of olanzapine was compared in three groups: patients treated with olanzapine (n = 134), patients treated with olanzapine plus fluvoxamine (n = 10) concomitantly, and patients treated with olanzapine plus sertraline (n = 21) concomitantly. No significant difference was seen between the olanzapine and the olanzapine plus sertraline groups. Patients receiving fluvoxamine in addition to olanzapine had C/D ratios that were in the mean 2.3-fold higher than patients receiving olanzapine without additional fluvoxamine. This indicated that fluvoxamine inhibits the metabolism of olanzapine, probably because of inhibition of cytochrome P450 (CYP) 1A2, whereas sertraline is unlikely to interfere with the metabolism of olanzapine. Combination therapy of olanzapine and fluvoxamine should be used cautiously, and therapeutic drug monitoring should be instituted to avoid olanzapine-induced adverse effects or intoxications  Fabrazzo M;La Pia S;Monteleone P;Mennella R;Esposito G;Pinto A;Maj M, J Clin Psychopharmacol, 2000, 20:708-710; Fluvoxamine increases plasma and urinary levels of clozapine and its major metabolites in a time- and dose-dependent manner Fluvoxamine increases plasma and urinary levels of clozapine and its major metabolites in a time- and dose-dependent manner Koponen HJ;Leinonen E;Lepola U, Eur Neuropsychopharmacol, 1996, 6:69-71; Fluvoxamine increases the clozapine serum levels significantly In this case report we describe an interaction between clozapine and fluvoxamine in two physically healthy patients meeting the DSM-IIIR criteria for paranoid schizophrenia. The substantial rise of clozapine serum levels suggest that caution should be exercised when combining fluvoxamine with clozapine as the clozapine concentration may increase by a factor of 5-10 Olesen OV;Linnet K, J Clin Psychopharmacol, 2000, 20:35-42; Fluvoxamine-Clozapine drug interaction: inhibition in vitro of five cytochrome P450 isoforms involved in clozapine metabolism Administration of fluvoxamine to patients receiving clozapine therapy may increase the steady-state serum concentrations of clozapine by a factor of 5 to 10. The authors undertook in vitro studies to disclose the mechanism behind this clinically important interaction. In a human liver microsome preparation, fluvoxamine showed a concentration-dependent inhibition of clozapine N-demethylation. Fluvoxamine was much less effective as an inhibitor of clozapine N-oxidation. Fluvoxamine also inhibited in a concentration-dependent manner the activity of all five cytochrome P450 (CYP) isoforms previously determined to be capable of catalyzing the demethylation of clozapine. Fluvoxamine inhibited CYP1A2 and 2C19 with the highest affinities (Ki values of 0.041 and 0.087 microM, respectively). The Ki values for CYP2C9 and 2D6 were 2.2 and 4.9 microM, respectively, whereas the Ki for CY3A4 was 24 microM. Assuming a hepatic tissue concentration of fluvoxamine in the range of 4 to 7 microM under therapeutic conditions, a clinically significant inhibition of all but CYP3A4 is expected in relation to clozapine N-demethylation. No significant effect of fluvoxamine on clozapine N-oxidation is to be expected under therapeutic conditions. Because of the large interindividual variability of the quantity of the various CYP isoforms in liver tissue, it is not possible to predict the fluvoxamine-induced increase in the plasma concentration of clozapine of an individual patient  SPC for serdolect, Produktresume, 2014; H. Lundbeck A/S http://www.produktresume.dk/docushare/dsweb/GetRendition/Document-22179/html Al-Chekakie MO;Ketz JM;Whinney CM, J Clin Psychopharmacol, 2006, 26(3): 332-333-333; Hypothermia in a patient receiving risperidone and paroxetine [2] Waade RB;Christensen H;Rudberg I;Refsum H;Hermann M, Ther Drug Monit, 2009, 31:233-238; Influence of comedication on serum concentrations of aripiprazole and dehydroaripiprazole Aripiprazole, a relatively new antipsychotic drug, is metabolized by cytochrome P450 3A4 (CYP3A4) and CYP2D6 to an active metabolite, dehydroaripiprazole. As studies on pharmacokinetic drug interactions with aripiprazole are so far limited, the aim of the present study was to investigate the impact of comedication on serum concentrations of aripiprazole and dehydroaripiprazole in psychiatric patients in a clinical setting. A therapeutic drug monitoring database was screened for patients receiving aripiprazole tablets as part of their treatment. Of the 361 samples included, 78% were from patients receiving comedication. The remaining 79 samples constituted the control group. Steady-state dose-adjusted serum concentrations (concentration to dose ratios, C:D ratios) of aripiprazole, dehydroaripiprazole and the sum of aripiprazole and dehydroaripiprazole, and the metabolic ratio (dehydroaripiprazole/aripiprazole) in the different comedication groups were compared with controls. Coadministration of a CYP3A4 inducer resulted in approximately 60% lower mean C:D ratios of aripiprazole, dehydroaripiprazole, and the sum of aripiprazole and dehydroaripiprazole (P < 0.05, P < 0.01, and P < 0.01, respectively). Combination with a CYP2D6 inhibitor resulted in a 45% higher mean C:D ratio of aripiprazole (P < 0.05), with no effect on the C:D ratio of dehydroaripiprazole. When aripiprazole was coadministered with alimemazine or lithium, a 56% (P < 0.01) and 43% (P = 0.05) higher mean C:D ratio of aripiprazole, respectively, was observed. Olanzapine, risperidone injections, escitalopram, or lamotrigine also had statistically significant effects on aripiprazole disposition but to a lesser extent. In conclusion, concurrent treatment with CYP3A4 inducers, CYP2D6 inhibitors, alimemazine, or lithium resulted in changes in the systemic exposure of aripiprazole between 40% and 60%. This is of such a magnitude that dose adjustments of aripiprazole may be required  Gossen D;de Suray JM;Vandenhende F;Onkelinx C;Gangji D, AAPS PharmSci, 2002, 4:E11; Influence of fluoxetine on olanzapine pharmacokinetics Conventional antidepressant treatment fails for up to 30% of patients with major depression. When there are concomitant psychotic symptoms, response rates are even worse. Thus, subsequent treatment often includes combinations of antidepressants or augmentation with antipsychotic agents. Atypical antipsychotic agents such as olanzapine cause fewer extrapyramidal adverse effects than conventional antipsychotics; for that reason, they are an advantageous augmentation strategy for treatment-resistant and psychotic depression. The purpose of this study was to assess the potential for pharmacokinetic interaction between olanzapine and fluoxetine, a popular antidepressant that is a selective serotonin reuptake inhibitor. The pharmacokinetics of 3 identical single therapeutic doses of olanzapine (5 mg) were determined in 15 healthy nonsmoking volunteers. The first dose of olanzapine was taken alone, the second given after a single oral dose of fluoxetine (60 mg), and the third given after 8 days of treatment with fluoxetine 60 mg, qd. Olanzapine mean Cmax was slightly higher (by about 18%) and mean CL/F was slightly lower (by about 15%) when olanzapine was coadministered with fluoxetine in single or multiple doses. Olanzapine mean t((1/2)) and median t(max) did not change. Although the pharmacokinetic effects of fluoxetine on olanzapine were statistically significant, the effects were small and are unlikely to modify olanzapine´s safety profile. The mechanism of influence is consistent with an inhibition of CYP2D6, which is known to control a minor pathway of olanzapine metabolism  Spina E;Avenoso A;Scordo MG;Ancione M;Madia A;Gatti G;Perucca E, J Clin Psychopharmacol, 2002, 22:419-423; Inhibition of risperidone metabolism by fluoxetine in patients with schizophrenia: a clinically relevant pharmacokinetic drug interaction The effect of fluoxetine on the steady-state plasma concentrations of risperidone and its active metabolite 9-hydroxyrisperidone (9-OH-risperidone) was evaluated in 10 patients with schizophrenia or schizoaffective disorder. Patients stabilized on risperidone (4-6 mg/day) received additional fluoxetine (20 mg/day) to treat concomitant depression. One patient dropped out after 1 week due to the occurrence of akathisia associated with markedly increased plasma risperidone concentrations. In the other subjects, mean plasma concentrations of risperidone increased during fluoxetine administration from 12 +/- 9 ng/mL at baseline to 56 +/- 31 at week 4 (p < 0.001), while the levels of 9-OH-risperidone were not significantly affected. After 4 weeks of combined treatment, the levels of the active moiety (sum of the concentrations of risperidone and 9-OH-risperidone) increased by 75% (range, 9-204%, p < 0.01) compared with baseline. The mean plasma risperidone/9-OH-risperidone ratio also increased significantly. During the second week of adjunctive therapy, two patients developed Parkinsonian symptoms, which were controlled with anticholinergic medication. These findings indicate that fluoxetine, a potent inhibitor of the cytochrome P450 enzyme CYP2D6 and a less potent inhibitor of CYP3A4, reduces the clearance of risperidone by inhibiting its 9-hydroxylation or alternative metabolic pathways. This interaction may lead to toxic plasma risperidone concentrations. In addition to careful clinical observation, monitoring plasma risperidone levels may be of value in patients given adjunctive therapy with fluoxetine  Chang WH;Augustin B;Lane HY;ZumBrunnen T;Liu HC;Kazmi Y;Jann MW, Psychopharmacology (Berl), 1999, 145:91-98; In-vitro and in-vivo evaluation of the drug-drug interaction between fluvoxamine and clozapine The drug-drug interaction between fluvoxamine (FLV) and clozapine (CLZ) was evaluated by in-vitro and in-vivo methods. In-vitro studies were conducted using human hepatic microsomal preparations with standard chemical inhibitors of the cytochrome P450 (CYP 450) isozyme system. Furafyline, FLV, troleandomycin (TAO) and erythromycin were used as the chemical inhibitors. For the in-vivo study, nine male schizophrenic patients were administered a single dose of CLZ 50 mg on two separate occasions with a 2-week FLV treatment of 50 mg twice a day in between each CLZ dose. Blood samples were obtained over 48 h following CLZ administration. CLZ and its two principle metabolites, clozapine N-oxide (CNO) and desmethylclozapine (DCLZ), were measured by high performance liquid chromatography with ultraviolet detection for both in-vitro and in-vivo studies. The in-vitro formation of DCLZ was inhibited by furafyline and FLV by 42.0% and 48.5% (P<0.01), respectively. TAO and erythromycin had only modest inhibition effects on DCLZ formation of 18.3% and 21.0% (P = NS), respectively. CNO in-vitro formation was significantly reduced by TAO and erythromycin by 44.5% and 45.0% (P<0.01), respectively. Furafyline and FLV had only modest effects of 19.2% and 8.5% (P = NS), respectively. In schizophrenic patients, FLV resulted in a pronounced increased in CLZ plasma concentrations with the total mean CLZ AUC increased by a factor of 2.58 from 780.8 ng/ml per hour to 2218.0 ng/ml per hour (P<0.001). All patients were sedated during combined FLV and CLZ use. During FLV treatment, CNO and DCLZ AUC both decreased by 18.8% (P = 0.07) and 9.0% (P = NS), respectively. These results indicate that in-vitro evaluations may not always accurately reflect changes in drug-drug interaction observed in-vivo. Careful patient monitoring is recommended during FLV/CLZ co-administration  Eggert AE;Crismon ML;Dorson PG, J Clin Psychiatry, 1994, 55:454-455; Lack of effect of fluoxetine on plasma clozapine concentrations Lack of effect of fluoxetine on plasma clozapine concentrations Albers LJ;Ozdemir V;Marder SR;Raggi MA;Aravagiri M;Endrenyi L;Reist C, J Clin Psychopharmacol, 2005, 25:170-174; Low-dose fluvoxamine as an adjunct to reduce olanzapine therapeutic dose requirements: A prospective dose-adjusted drug interaction strategy Despite the advances in antipsychotic pharmacotherapy over the past decade, many atypical antipsychotic agents are not readily accessible by patients with major psychosis or in developing countries where the acquisition costs may be prohibitive. Olanzapine is an efficacious and widely prescribed atypical antipsychotic agent. In theory, olanzapine therapeutic dose requirement may be reduced during concurrent treatment with inhibitors of drug metabolism. In vitro studies suggest that smoking-inducible cytochrome P450 (CYP) 1A2 contributes to formation of the metabolite 4'-N-desmethylolanzapine. The present prospective study tested the hypothesis that olanzapine steady-state doses can be significantly decreased by coadministration of a low subclinical dose of fluvoxamine, a potent inhibitor of cytochrome P450 1A2. The study design followed a targeted 'at-risk' population approach with a focus on smokers who were likely to exhibit increased cytochrome P450 1A2 expression. Patients with stable psychotic illness (N = 10 men, all smokers) and receiving chronic olanzapine treatment were evaluated for steady-state plasma concentrations of olanzapine and 4'-N-desmethylolanzapine. Subsequently, olanzapine dose was reduced from 17.5 ± 4.2 mg/d (mean ± SD) to 13.0 ± 3.3 mg/d, and a nontherapeutic dose of fluvoxamine (25 mg/d, PO) was added to regimen. Patients were reevaluated at 2, 4, and 6 weeks during olanzapine-fluvoxamine cotreatment. There was no significant change in olanzapine plasma concentration, antipsychotic response, or metabolic indices (eg, serum glucose and lipids) after dose reduction in the presence of fluvoxamine (P > 0.05). 4'-N-desmethylolanzapine/olanzapine metabolic ratio decreased from 0.45 ± 0.20 at baseline to 0.25 ± 0.11 at week 6, suggesting inhibition of the cytochrome P450 1A2-mediated olanzapine 4'-N-demethylation by fluvoxamine (P < 0.05). In conclusion, this prospective pilot study suggests that a 26% reduction in olanzapine therapeutic dose requirement may be achieved by coadministration of a nontherapeutic oral dose of fluvoxamine. Copyright < copyright > 2005 by Lippincott Williams & Wilkins  Matsumoto R;Kitabayashi Y;Nakatomi Y;Tsuchida H;Fukui K, Am J Psychiatry, 2005, 162:812-812; Neuroleptic malignant syndrome induced by quetiapine and fluvoxamine Taylor D, Br J Psychiatry, 1997, 171:109-112; Pharmacokinetic interactions involving clozapine BACKGROUND: Metabolism of clozapine is complex and not fully understood. Pharmacokinetic interactions with other drugs have been described but, in some cases, their mechanism is unknown. METHOD: Published trials and case reports relevant to the human metabolism of clozapine and to suspected pharmacokinetic interactions were reviewed. RESULTS: Metabolism of clozapine appears to be largely controlled by the function of the hepatic cytochrome p450IA2 (CYPIA2). Compounds which induce CYPIA2 activity (carbamazepine, tobacco smoke) may reduce plasma clozapine levels. Inhibitors of CYPIA2 (caffeine, erythromycin) have the opposite effect. Drugs which inhibit the hepatic cytochrome p4502D6 (CYP2D6) have also been reported to elevate plasma clozapine levels. The mechanism of this interaction is unclear. CONCLUSIONS: The co-administration of clozapine and compounds reported to alter its metabolism should be avoided where possible. A host of other interactions can be predicted and so caution should be exercised when co-administering drugs which affect the function of CYPIA2 and CYP2D6. The pharmacokinetics of clozapine require further investigation so that its safe use can be assured  Wetzel H;Anghelescu I;Szegedi A;Wiesner J;Weigmann H;Harter S;Hiemke C, J Clin Psychopharmacol, 1998, 18:2-9; Pharmacokinetic interactions of clozapine with selective serotonin reuptake inhibitors: differential effects of fluvoxamine and paroxetine in a prospective study Pharmacokinetic interactions of clozapine and its metabolites N-desmethylclozapine and clozapine N-oxide with the selective serotonin reuptake inhibitors (SSRIs) fluvoxamine and paroxetine were investigated in a prospective study in schizophrenic patients under steady-state conditions. Thirty patients were treated with clozapine at a target dose of 2.5 to 3.0 mg/kg of body weight. After gradual dose escalation, serum concentrations of clozapine and two metabolites were determined twice at 7-day intervals after steady-state conditions had been reached. Then, fluvoxamine (50 mg/day) or paroxetine (20 mg/day) was added in 16 and 14 patients, respectively. Serum concentrations of clozapine and its metabolites were measured after 1, 7, and 14 days of coadministration with the SSRI. Mean trough concentrations of steady-state serum concentrations of clozapine, N-desmethylclozapine, and clozapine N-oxide were markedly elevated under fluvoxamine by about threefold of baseline concentrations whereas paroxetine induced only minor, nonsignificant changes. Estimation of the mean elimination half-life of clozapine 2 weeks after start of fluvoxamine comedication revealed an increase from 17 hours to about 50 hours whereas there was no change under paroxetine coadministration. The N-desmethylclozapine/clozapine ratio did not change significantly with either SSRI. Under monotherapy, clozapine mean serum concentrations in smokers were significantly lower by 32% compared with nonsmokers. Similarly, N-demethylation ratios were about 20 to 50% higher in smokers. Thus, in all patients, fluvoxamine induced relevant increases in serum concentrations of clozapine and its metabolites, probably by the inhibition of enzymes catalyzing the degradation of clozapine and N-desmethylclozapine, whereas paroxetine, at a usual clinically effective dosage of 20 mg/day, did not cause significant pharmacokinetic interactions  Spina E;Avenoso A;Salemi M;Facciola G;Scordo MG;Ancione M;Madia A, Pharmacopsychiatry, 2000, 33:213-217; Plasma concentrations of clozapine and its major metabolites during combined treatment with paroxetine or sertraline The effect of paroxetine or sertraline on steady-state plasma concentrations of clozapine and its major metabolites was studied in 17 patients with schizophrenia or schizoaffective disorder stabilized on clozapine therapy (200-400 mg/day). In order to treat negative symptomatology or concomitant depression, 9 patients received additional paroxetine (20-40mg/day) and 8 patients sertraline (50-100 mg/day). After 3 weeks of paroxetine administration, mean plasma concentrations of clozapine and norclozapine increased significantly by 31% (p<0.01) and by 20% (p<0.05), respectively, while levels of clozapine N-oxide remained almost unchanged. The mean plasma norclozapine/clozapine and clozapine N-oxide/clozapine ratios were not modified during paroxetine treatment. No significant changes in plasma concentrations of clozapine and its major metabolites were observed after 3 weeks of combined therapy with sertraline. Clozapine coadministration with either paroxetine or sertraline was well tolerated. Our findings suggest that the metabolism of clozapine is not affected by sertraline treatment at typical therapeutic doses, while paroxetine, a potent inhibitor of CYP2D6, appears to inhibit the metabolism of clozapine, possibly by affecting pathways other than N-demethylation and N-oxidation. While sertraline may be added safely to patients on maintenance treatment with clozapine, careful clinical observation and monitoring of plasma clozapine levels may be useful whenever paroxetine is coadministered with clozapine  Spina E;Avenoso A;Facciola G;Scordo MG;Ancione M;Madia A, Ther Drug Monit, 2001, 23:223-227; Plasma concentrations of risperidone and 9-hydroxyrisperidone during combined treatment with paroxetine SUMMARY: The effects of paroxetine on steady-state plasma concentrations of risperidone and its active metabolite 9-hydroxyrisperidone (9-OH-risperidone) were studied in 10 patients with schizophrenia or schizoaffective disorder. Patients stabilized using risperidone therapy (4-8 mg/d) also received paroxetine (20 mg/d) for 4 weeks. During paroxetine administration, mean plasma concentrations of risperidone increased significantly (P < 0.01), whereas levels of 9-OH-risperidone decreased slightly but not significantly. After 4 weeks of paroxetine treatment, the sum of the concentrations of risperidone and 9-OH-risperidone (active moiety) increased significantly by 45% (P < 0.05) over baseline. The mean plasma risperidone/9-OH-risperidone ratio was also significantly modified (P < 0.001) during paroxetine treatment. The drug combination was generally well tolerated with the exception of one patient who developed Parkinsonian symptoms in the second week of adjunctive therapy. In this patient total plasma levels of risperidone and its active metabolite increased by 62% during paroxetine co-administration. The authors´ findings indicate that paroxetine, a potent inhibitor of CYP2D6, may impair the elimination of risperidone, primarily by inhibiting CYP2D6-mediated 9-hydroxylation and to a lesser extent by simultaneously affecting the further metabolism of 9-OH-risperidone or other pathways of risperidone biotransformation. Careful clinical observation and possibly monitoring of plasma risperidone levels may be useful whenever paroxetine is co-administered with risperidone  Castberg I;Skogvoll E;Spigset O, J Clin Psychiatry, 2007, b, 68:1540-1545; Quetiapine and drug interactions: evidence from a routine therapeutic drug monitoring service OBJECTIVE: The objective of the present study was to investigate the effect of age, gender, and various comedications on the pharmacokinetics of quetiapine in a naturalistic setting. METHOD: In total, 2111 serum samples analyzed for quetiapine during the period from June 2001 to December 2004 were included in the study. The samples had been collected for routine therapeutic drug monitoring purposes from 1179 patients treated with quetiapine. A log-linear mixed model was used to identify factors influencing the dose-corrected quetiapine serum concentration, expressed as the quetiapine concentration-to-dose (C/D) ratio. Variables included in the analysis were age, gender, and concomitant treatment with a total of 41 drugs most often used in combination with quetiapine. RESULTS: Age >or= 70 years (p = .001) and comedication with alimemazine (p = .002), fluvoxamine (p = .001), citalopram/escitalopram (p = .041), or clozapine (p < .001) significantly increased the serum concentrations of quetiapine, while age < 18 years (p = .044) and comedication with lamotrigine (p = .024), levomepromazine (p = .011), oxazepam (p < .001), or carbamazepine (p < .001) significantly decreased the serum concentrations. The effects were most pronounced for fluvoxamine (+159%), clozapine (+82%), age >or= 70 years (+67%), and carbamaze-pine (-86%). In 18% of the samples, the daily dose exceeded the currently recommended maximum of 800 mg/day. CONCLUSION: Due to the increased serum levels of quetiapine, a lower dose than usual should be considered when quetiapine is administered to elderly patients and to patients comedicated with clozapine or fluvoxamine. As the inducing effect of carbamazepine on quetiapine metabolism is very potent, cotreatment with carbamazepine cannot be recommended. On the basis of our data and pharmacokinetic considerations, the majority of drugs commonly used in psychiatry can safely be given in combination with quetiapine  Barnhill J;Susce MT;Diaz FJ;De LJ, Pharmacopsychiatry, 2005, 38(5): 223-225-225; Risperidone half-life in a patient taking paroxetine: A case report This case report further establishes the inhibitory effects of paroxetine on risperidone (R) metabolism in a patient whose R was discontinued due to side effects. Baseline through levels in ng/ml were 33 for R, 9 for 9-hydroxyrisperidone (9-OHR) and 42 for the total moiety. The fourth morning after R discontinuation, levels were 4 for R, 1 for 9-OHR and 5 for the total moiety. The estimated half-lives were 23.8 hours for R, 22.8 hours for 9-OHR and 23.5 hours for the total moiety. < copyright > Georg Thieme Verlag KG Stuttgart Centorrino F;Baldessarini RJ;Frankenburg FR;Kando J;Volpicelli SA;Flood JG, Am J Psychiatry, 1996, 153:820-822; Serum levels of clozapine and norclozapine in patients treated with selective serotonin reuptake inhibitors : The selectiOBJECTIVEve serotonin reuptake inhibitor (SSRI) fluoxetine can increase serum levels of clozapine and norclozapine, but effects of other SSRIs are unknown. Thus, the authors evaluated interactions of clozapine with fluoxetine, paroxetine, and sertraline. METHOD: Serum clozapine and norclozapine concentrations were assayed in 80 psychiatric patients, matched for age and clozapine dose, given clozapine (mean dose = 279 mg/day) alone or with fluoxetine (mean dose = 39.3 mg/day), paroxetine (mean = 31.2 mg/day), or sertraline (mean = 92.5 mg/ day). Each patient´s dose of clozapine was stable for at least a month before serum sampling. RESULTS: Concentrations of clozapine plus norclozapine averaged 43% higher, and the risk of levels higher than 1000 ng/ml was 10-fold greater (25%), in the patients taking SSRIs, with minor differences between patients taking the individual SSRIs. CONCLUSIONS: SSRIs can increase circulating concentrations of clozapine and norclozapine, sometimes to potentially toxic levels  SmPC for RXULTI, Produktresume, 2025; SmPC for RXULTI https://www.ema.europa.eu/da/documents/product-information/rxulti-epar-product-information_da.pdf SPC for Sycrest, Produktresume, 2013; Sycrest (asenapin), resoribletter, sublinguale Wang CY;Zhang ZJ;Li WB;Zhai YM;Cai ZJ;Weng YZ;Zhu RH;Zhao JP;Zhou HH, J Clin Pharmacol, 2004, 44:785-792; The differential effects of steady-state fluvoxamine on the pharmacokinetics of olanzapine and clozapine in healthy volunteers The combination of atypical antipsychotics and selective serotonin reuptake inhibitors is an effective strategy in the treatment of certain psychiatric disorders. However, pharmacokinetic interactions between the two classes of drugs remain to be explored. The present study was designed to determine whether there were different effects of steady-state fluvoxamine on the pharmacokinetics of a single dose of olanzapine and clozapine in healthy male volunteers. One single dose of 10 mg olanzapine (n = 12) or clozapine (n = 9) was administered orally. Following a drug washout of at least 4 weeks, all subjects received fluvoxamine (100 mg/day) for 9 days, and one single dose of 10 mg olanzapine or clozapine was added on day 4. Plasma concentrations of olanzapine, clozapine, and N-desmethylclozapine were assayed at serial time points after the antipsychotics were given alone and when added to fluvoxamine. No bioequivalence was found in olanzapine alone and cotreatment with fluvoxamine for the mean peak plasma concentration (C(max)), the area under the concentration-time curve from time 0 to last sampling time point (AUC(0-t)), and from time 0 to infinity (AUC(0- infinity )). Under the cotreatment, C(max) of olanzapine was significantly elevated by 49%, with a 32% reduced time (t(max)) to C(max), whereas the C(max) and t(max) of clozapine were unaltered. The cotreatment increased the AUC(0-t) and AUC(0- infinity ) of olanzapine by 68% and 76%, respectively, greater than those of clozapine (40% and 41%). The presence of fluvoxamine also prolonged the elimination half-life (t(1/2)) of olanzapine by 40% and, to a much greater extent, clozapine by 370% but reduced the total body clearance (CL/F) of clozapine (78%) more significantly than it did for olanzapine (42%). The apparent volume of distribution (V(d)) was suppressed by 31% in olanzapine combined with fluvoxamine but was unaltered in the clozapine regimen. A significant reduction in the N-desmethylclozapine to clozapine ratio was present in the clozapine with fluvoxamine regimen. The effects of fluvoxamine on different aspects of pharmacokinetics of the two antipsychotics may have implications for clinical therapeutics  Bondolfi G;Eap CB;Bertschy G;Zullino D;Vermeulen A;Baumann P, Pharmacopsychiatry, 2002, 35:50-56; The effect of fluoxetine on the pharmacokinetics and safety of risperidone in psychiatric patients In this open, 30-day trial, the pharmacokinetics, safety and tolerability of a combination therapy of risperidone (4 or 6 mg/day)and fluoxetine (20mg/day from day 6) were evaluated in 11 psychotic inpatients. CYP2D6 genotyping revealed that 3 and 8 patients were poor metabolizers (PMs) and extensive metabolizers (EMs) of debrisoquine, respectively. The mean (+/- SD) AUC of risperidone increased from 83.1 +/- 46.8 ng.h/ml and 398.3 +/- 33.2 ng.h/ml (monotherapy) to 345.1 +/- 158.0 ng.h/ml (p < 0.05) and 514.0 +/- 144.2 ng.h/ml (p < 0.001) when coadministered with fluoxetine in EMs and PMs, respectively. The AUC of the active moiety (risperidone plus 9-hydroxy-risperidone) increased from 470.0 +/- 170.0 ng.h/ml to 663.0 +/- 243.3 ng.h/ml (p < 0.05)and from 576.3 +/- 19.6 ng.h/ml to 788.0 +/- 89.1 ng.h/ml (ns) in EMs and PMs, respectively. In EMs, the AUC of 9-hydroxy-risperidone remained similar (monotherapy vs. combination therapy: 386.8 +/- 153.0 ng.h/ml vs. 317.7 +/- 125.2 ng.h/ml, ns),whereas it increased in PMs (178.3 +/- 23.5 ng.h/ml vs. 274.0 +/- 55.1 ng.h/ml (p < 0.05)). Ten of the 11 patients showed a clinical improvement (reduction of 20% or more in total PANSS score and 70% on the mean MADRS score compared to baseline). The severity and incidence of extrapyramidal symptoms and adverse events did not significantly increase when fluoxetine was added  Berwaerts J;Cleton A;Herben V;van dV;Chang I;van HP;Eerdekens M, Pharmacopsychiatry, 2009, 42:158-163; The effects of paroxetine on the pharmacokinetics of paliperidone extended-release tablets INTRODUCTION: Co-morbid medical and psychiatric conditions are common in individuals with schizophrenia. As such, selecting antipsychotic medications with a low potential for drug-drug interactions (DDIs) is crucial, as many are extensively metabolized by hepatic cytochrome P450 (CYP) isozymes. METHODS: This randomized, crossover study examined the effects of paroxetine (a potent CYP2D6 inhibitor) on the pharmacokinetic parameters of a single dose of the novel antipsychotic agent, paliperidone extended-release tablets (paliperidone ER), in healthy subjects. RESULTS: The mean C (max) and AUC of paliperidone were slightly higher and paliperidone clearance was slightly lower following co-administration of paliperidone ER with paroxetine. There was a ratio of geometric treatment means of 116.48% for AUC (infinity) [90% CI: 104.49-129.84]. However, the increase in total exposure to paliperidone was not considered clinically relevant. The incidence of adverse events was lower when subjects received the combination of paliperidone ER and paroxetine compared with paroxetine alone. DISCUSSION: Results suggest that no clinically relevant pharmacokinetic interaction occurs when paroxetine and paliperidone ER are co-administered and, therefore, initiation or discontinuation of concomitant treatment with CYP2D6-inhibiting drugs does not appear to warrant an adjustment in paliperidone ER dosage  Boulton DW;Balch AH;Royzman K;Patel CG;Berman RM;Mallikaarjun S;Reeves RA, J Psychopharmacol, 2010, 24:537-546; The pharmacokinetics of standard antidepressants with aripiprazole as adjunctive therapy: Studies in healthy subjects and in patients with major depressive disorder Possible effects of the atypical antipsychotic aripiprazole on the pharmacokinetics of standard antidepressant therapies (ADTs) were assessed in two open-label, non-randomised studies in healthy subjects (Studies 1 and 2) and two placebo-controlled studies in patients with major depressive disorder (MDD) (Studies 3 and 4). Healthy subjects received venlafaxine 75 mg/day (Study 1; N = 38) or escitalopram 10 mg/ day (Study 2; N = 25) with the addition of aripiprazole 10-20 mg/day (10 mg/day fixed dose in Study 2) for 14 days. Patients with MDD (N = 498; Studies 3 and 4) received escitalopram (10-20 mg/day), fluoxetine (20-40 mg/day), paroxetine controlled-release (37.5-50 mg/day), sertraline (100-150 mg/day) or venlafaxine extended-release (150-225 mg/day) for 8 weeks plus placebo. Incomplete responders were randomised (1:1) to placebo or adjunctive aripiprazole 2-20 mg/day. Blood samples were collected for pharmacokinetic analysis of ADTs. Plasma concentration-time data from Studies 3 and 4 were combined for statistical analysis. In healthy subjects, point estimates [90% CI] for the ratios of geometric means of Cmax (venlafaxine 1.148 [1.083-1.217]; escitalopram 1.04 [0.99-1.09]) and AUC TAU (venlafaxine 1.183 [1.130-1.238]; escitalopram 1.07 [1.04-1.11]) indicated no meaningful increase in ADT exposure in the presence of aripiprazole. In patients, point estimates for mean plasma concentration ratios indicated no substantial effect of aripiprazole on any ADT escitalopram 0.970 [0.911-1.033], fluoxetine 1.177 [1.049-1.321], paroxetine 0.730 [0.598-0.892], sertraline 0.958 [0.887-1.035] or venlafaxine 0.966 [0.887-1.051]. Aripiprazole had no meaningful effects on the pharmacokinetics of standard ADTs in either healthy subjects or patients with MDD. copyright 2010 British Association for Psychopharmacology  Blaschke D;Parwani AS;Huemer M;Rolf S;Boldt LH;Dietz R;Haverkamp W, Pharmacopsychiatry, 2007, 40:294-295; Torsade de pointes during combined treatment with risperidone and citalopram Ozdemir V;Kalow W;Okey AB;Lam MS;Albers LJ;Reist C;Fourie J;Posner P;Collins EJ;Roy R, J Clin Psychopharmacol, 2001, 21:603-607; Treatment-resistance to clozapine in association with ultrarapid CYP1A2 activity and the C-->A polymorphism in intron 1 of the CYP1A2 gene: effect of grapefruit juice and low-dose fluvoxamine Antipsychotic response to clozapine varies markedly among patients with schizophrenia. The disposition of clozapine is dependent, in part, on the cytochrome P-450 (CYP) 1A2 enzyme in vivo. In theory, a very high CYP1A2 activity may lead to subtherapeutic concentrations and treatment resistance to clozapine. This prospective case study evaluates the clinical significance of ultrarapid CYP1A2 activity and a recently discovered single nucleotide (C --> A) polymorphism in intron 1 of the CYP1A2 gene (CYP1A2*F) for treatment resistance to clozapine. In addition, we describe the effect of grapefruit juice or low-dose fluvoxamine (25-50 mg/d) coadministration on clozapine and active metabolite norclozapine steady-state plasma concentration and antipsychotic response Chong SA;Tan CH;Lee HS, J Clin Psychopharmacol, 1997, 17:68-69; Worsening of psychosis with clozapine and selective serotonin reuptake inhibitor combination: two case reports

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