Cytochrome P450 : Alphabetical drug list
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1A2 2C9 2C19 2D6 2E1 3A4
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Drug CYP interaction Clinical consequences
famciclovir NOT metabolised by CYP safe with eg cyclosporine [Drug Metab Dispos 1993 Jan-Feb;21(1):18-23]
felbamate (no significant interaction with lamotrigine, clonazepam, vigabatrin. {may inhibit beta oxidation of valproate} 2E1 : METABOLISM interaction potential
3A4 : metabolism (normally minor) 3A4 inducers lower levels
3A4 : induces (!) lowers levels of carbamazepine, gestodene
2C19 : inhibits lowers phenytoin clearance
famotidine does NOT interact with CYP -
felodipine (Ca channel blocker) CYP3A4 : metabolism
{inhibition of 3A4 is probably clinically insignificant}
interaction with 3A4 inhibitors (eg grapefruit juice, erythromycin ), inducers;
fenfluramine : ? as for dexfenfluramine
fenofibrate (see fibrates) 3A4 potential for interaction with e.g. 3A4 inhibitors
fentanyl CYP2D6 : metabolism ?
CYP3A4 : METABOLISM (to norfentanyl) NO significant interaction with paracetamol or itraconazole ; ritonavir inhibits its metabolism; fentanyl competitively inhibits midazolam metabolism!
fexofenadine (nonsedating antihistamine, cf loratadine) 3A4 : METABOLISM significant interaction with inhibitors eg. troglitazone although fexofenadine "doesn't have cardiac effects"
"Fibrates" (fibric acid derivatives) (gemfibrozil, fenofibrate, bezafibrate, ciprofibrate) 3A4 : METABOLISM potential for interaction with 'statins', warfarin, cyclosporin and oral hypoglycaemic agents (metformin, tolbutamide, glibenclamide..)
finasteride 3A4 : substrate ?
flecainide CYP2D6 : metabolism ? significant effect of 2D6 polymorphism see [Clin Pharmacol Ther 1994 Mar;55(3):256-69]
2D6 : INHIBITION (IC50 0.44 µmol) ?
1A2 : mild inhibition ?
2C9 : INHIBITION (IC50 = 49 µmol) ?
fluconazole See alsoazole antifungals 2C9 : INHIBITS (potent) 'clinically significant' - phenytoin, warfarin, sulphamethoxazole, losartan [Clin Pharmacokinet 2000 Feb;38(2):111-80]
3A4 : INHIBITS potential for significant interactions eg carbamazepine
2C19 : INHIBITS Of uncertain relevance!
fluorouracil (5-fluorouracil, 5FU, 5-FU) 2C9 : ? INHIBITS warfarin toxicity [Chemotherapy 1999 Sep-Oct;45(5):392-5]
fluoxetine (See also SSRIs)
metabolised to norfluoxetine
CYP2C9 : metabolism ?
CYP2D6 : metabolism : interaction potential
2D6 : INHIBITS (potent) many interactions e.g. may increase perphenazine, haloperidol, thioridazine and risperidone, metoprolol levels
3A4 : inhibits ? interaction with alprazolam, midazolam, carbamazepine
parkinsonism reported due to toxicity when given with cimetidine [J Geriatr Psychiatry Neurol 1995 Oct;8(4):231-3]!
fluphenazine 2D6 : metabolism and inhibition (Ki 9.4µM) ?
flurbiprofen (NSAID) 2C9 : metabolism (alone) interaction potential
flutamide (androgen receptor antagonist) 3A4 - metabolism ?
1A2 : METABOLISM [Drug Metab Dispos 1997 Nov;25(11):1298-303] Interation with imipramine, caffeine, estradiol; the metabolite 2-hydroxyflutamide inhibits 1A2! Also, metabolites may be hepatotoxic.
fluvastatin (See also HMG Co-A reductase inhibitors) 2C9 : INHIBITS, Ki 0.3 to 0.5 µM interaction potential
2C9: METABOLISM (the main route) ?
fluvoxamine {inhibition: 1A2 > 2C19 > 2D6 > 1A1 } CYP2C19 : INHIBITS (Ki 0.7 - 4.7 µmol) potential interaction with imipramine, clomipramine, amitriptyline, diazepam, proguanil (high levels) [Eur J Clin Pharmacol 1998 Nov-Dec;54(9-10):735-40]
CYP1A2 : minor substrate ?
1A2 : INHIBITS (0.2µmol) ? interaction potential
2D6 : metabolism (? mild inhibition - Xu says 'no' [Br J Clin Pharmacol 1996 Oct;42(4):518-21]) ?
3A4 : INHIBITS raised methadone concentrations, interaction with cyclosporine

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1A2 2C9 2C19 2D6 2E1 3A4

Page author: jo@anaesthetist.com Last update: 2000-6-22