PHARMACOGENETIC CONSIDERATIONS FOR PSYCHOTROPIC DRUGS
Generic Brand Pharmaco-
genomic
Biomarker
Section Genetic Notes
aripiprazole Abilify CYP2D6 Dosage and admin Poor metabolizers (PMs): initially reduce dose to ½ the usual dose; adjust based on clinical response. Concomitant strong CYP3A4 inhibitors: reduce aripiprazole dose to ¼ the usual dose.
Abilify Maintena Dosage and admin PMs: 300mg once monthly. Concomitant CYP3A4 inhibitors: 200mg once monthly. See full labeling.
atomoxetine Strattera CYP2D6 Dosage and admin, Warning/
Precaution, Interactions, Clinical 
pharmacology
Children and adolescents (PMs ≤70kg) or concomitant strong CYP2D6 inhibitors: initially 0.5mg/kg/day; titrate to usual target dose of 1.2mg/kg/day after 4wks if needed.
Children and adolescents (PMs >70kg) or concomitant strong CYP2D6 inhibitors in adults: initially 40mg/day; titrate to usual target dose of 80mg/day after 4wks if needed.
brexpiprazole Rexulti CYP2D6 Dosage and admin PMs: ½ of usual dose. Concomitant moderate/strong CYP3A4 inhibitors: ¼ of usual dose.
carbama
zepine
Equetro HLA‑B*1502 Boxed Warning, Warning/
Precaution
Chinese ancestry: studies have found strong association between HLA‑B*1502 and the risk of developing SJS/TEN. Test for HLA-B*1502 prior to initiation; avoid use if positive for the HLA-B*1502 allele unless benefits clearly outweigh the risks of serious skin reactions.
Tegretol
citalopram Celexa CYP2C19, CYP2D6 Warning/
Precaution, Special populations, Clinical 
pharmacology
CYP2C19 PMs, concomitant cimetidine or other CYP2C19 inhibitors, hepatic impairment, or >60yrs: max 20mg/day due to the risk of QT prolongation.
CYP2D6 PMs and EMs: levels not significantly different.
clobazam Onfi CYP2C19 Dosage and admin PMs: initially 5mg/day; titrate according to weight but to ½ the usual dose, an additional titration to max dose (20mg/day or 40mg/day, depending on weight) may be started at Day 21.
chlordiaze
poxide/
amitriptyline
CYP2D6 Warning/
Precaution
PMs: normal metabolizers (NMs) may resemble PMs since certain drugs inhibit CYP2D6. Caution with concomitant SSRIs or when switching from one class to the other. Sufficient time (at least 5wks) must elapse before initiating TCAs in patients being withdrawn from fluoxetine. Concomitant CYP2D6 inhibitors: may need to adjust dose of either drug; if withdrawn, may need to increase TCA dose (monitor).
clomipramine Anafranil CYP2D6 Interactions See chlordiazepoxide/
amitriptyline.
clozapine Clozaril, FazaClo CYP2D6 Dosage and admin, Special populations, Clinical 
pharmacology
PMs: may need to reduce dose. Increased clozapine levels possible since it’s completely metabolized and then excreted.
desipramine Norpramin CYP2D6 Interactions See chlordiazepoxide/
amitriptyline.
dextrometh
orphan/
quinidine
Nuedexta CYP2D6 Warning/
Precaution, Clinical 
pharmacology, Interactions
PMs: quinidine component does not contribute to the effectiveness of Nuedexta in PMs but a possible risk of significant toxicity is present. Consider genotyping to determine PM status prior to initiation.
doxepin Silenor CYP2D6, CYP2C19 Special populations PMs: may have higher doxepin plasma levels than NMs.
fluoxetine Prozac CYP2D6 Interactions, Clinical 
pharmacology
Concomitant drugs metabolized by CYP2D6 or narrow therapeutic index: NMs may resemble PMs since fluoxetine is a CYP2D6 inhibitor. Initiate lowest effective dose if receiving fluoxetine or have taken it in previous 5wks. If already taking drugs metabolized by CYP2D6 and fluoxetine is added afterwards, consider decreasing dose of original drug.
fluoxetine/
olanzapine
Symbyax CYP2D6 Clinical pharmacology See fluoxetine.
fluvoxamine CYP2D6 Interactions PMs: caution with fluvoxamine and other concomitant drugs known to inhibit CYP2D6.
galantamine Razadyne CYP2D6 Special populations, Clinical 
pharmacology
PMs: similar pharmacokinetics parameters compared to EMs. No dosage adjustment needed in PMs since the dose is individually titrated to tolerability.
iloperidone Fanapt CYP2D6 Dosage and admin, Clinical 
pharmacology
PMs: higher exposure to iloperidone vs. EMs. Reduce dose by ½. Lab tests are available to identify CYP2D6 PMs.
imipramine Tofranil CYP2D6 Interactions See chlordiazepoxide/
amitriptyline.
modafinil Provigil CYP2D6 Interactions, Clinical 
pharmacology
PMs: metabolism by CYP2C19 may be substantially increased. Provigil may cause elevation in tricyclic levels; may need to reduce dose of tricyclics.
nortriptyline Pamelor CYP2D6 Interactions See chlordiazepoxide/
amitriptyline.
perphenazine CYP2D6 Clinical 
pharmacology, Interactions
PMs: metabolize perphenazine slower and have higher concentrations vs. NMs or extensive metabolizers (EMs).
Elderly: PMs have higher plasma concentrations of antipsychotics at usual doses, which may correlate with the emergence of side effects. Prospective phenotyping prior to initiation may identify those at risk for adverse events.
pimozide Orap CYP2D6 Dosing and admin, Warning/
Precaution
Children (>0.05mg/kg/day): perform CYP2D6 genotyping. PMs: max 0.05mg/kg/day; should not increase dose earlier than 14 days.
Adults (doses >4mg/day): perform CYP2D6 genotyping. PMs: max 4mg/day; should not increase dose earlier than 14 days.
protriptyline Vivactil CYP2D6 Warning/
Precaution
See chlordiazepoxide/
amitriptyline.
risperidone Risperdal CYP2D6 Clinical pharmacology EMs and PMs have similar pharmacokinetics even though EMs convert risperidone to 9‑hydroxyrisperidone quicker than PMs.
Risperidone EMs half-life: 3hrs.
Risperidone PMs half life: 20hrs.
Overall mean half-life: 20hrs.
tetrabenazine Xenazine CYP2D6 Dosage and admin >50mg/day: perform CYP2D6 genotyping to determine PM or EM status prior to initiation. Individualize dose based on PM or EM status.
EMs or intermediate metabolizers (IMs): max 37.5mg/dose and 100mg/day.
PMs: max 25mg/dose and 50mg/day.
thioridazine CYP2D6 Contraindi
cations
Contraindicated in patients known to have a genetic defect leading to reduced CYP2D6 activity.
trimipramine Surmontil CYP2D6 Interactions See chlordiazepoxide/
amitriptyline.
valbenazine Ingrezza CYP2D6 Dosage and admin, Special populations PMs: consider reducing dose based on tolerability. Increased exposure to valbenazine’s active metabolite may increase risk of adverse reactions.
NOTES

Not an inclusive list of medications or pharmacogenomic details. Please see drug monograph at www.eMPR.com and/or contact company for full drug labeling.

(Rev. 4/2018)

This article originally appeared on MPR