ABSTRACT
OBJECTIVE: The aim of this study was to assess the drug interaction potential of psychotropic medication on methadone N-demethylation using cDNA-expressed cytochrome P450 CYP enzymes. METHODS: Methadone was incubated with various drugs (n = 10) and cDNA-expressed CYP3A4, CYP2D6, CYP2B6, CYP2C19 and CYP1A2 enzymes to screen for their inhibition potency. The nature of enzyme selective activity for inhibition was further investigated for potent inhibitors. To test for a mechanism-based component in inhibition, all substances were tested with preincubation and without. 2-Ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) concentration was determined by liquid chromatography/tandem mass spectrometry following liquid/liquid extraction. RESULTS: Formation of EDDP was catalysed by CYP3A4, CYP2D6 and CYP2C19. The N-demethylation of methadone was preferentially inhibited by amitriptyline, buprenorphine, methylenedioxymethamphetamine (MDMA) and zolpidem. Both amitriptyline and buprenorphine were strong, reversible inhibitors of CYP3A4. Similarly, amitriptyline and MDMA were identified as inhibitors of CYP2D6. Zolpidem revealed a mechanism-based inhibition of CYP3A4. CONCLUSION: Amitriptyline, MDMA and zolpidem are likely to slow down conversion of methadone and to increase its area under the curve (AUC). A consideration of the in vitro evidence of drug-methadone interactions should help to improve patient care during methadone maintenance treatment.
Subject(s)
Cytochrome P-450 Enzyme System/metabolism , Methadone/metabolism , Algorithms , Amitriptyline/metabolism , Amitriptyline/pharmacology , Analgesics, Opioid/metabolism , Analgesics, Opioid/pharmacology , Atomoxetine Hydrochloride , Chromatography, Liquid/methods , Citalopram/metabolism , Citalopram/pharmacology , Clozapine/metabolism , Clozapine/pharmacology , Cytochrome P-450 Enzyme Inhibitors , Cytochrome P-450 Enzyme System/genetics , Dose-Response Relationship, Drug , Drug Interactions , Isoenzymes/antagonists & inhibitors , Isoenzymes/genetics , Isoenzymes/metabolism , Kinetics , Methadone/pharmacology , Methylation , N-Methyl-3,4-methylenedioxyamphetamine/metabolism , N-Methyl-3,4-methylenedioxyamphetamine/pharmacology , Oxidoreductases, N-Demethylating/antagonists & inhibitors , Oxidoreductases, N-Demethylating/metabolism , Oxidoreductases, N-Demethylating/pharmacology , Propylamines/metabolism , Propylamines/pharmacology , Psychotropic Drugs/metabolism , Psychotropic Drugs/pharmacology , Pyridines/metabolism , Pyridines/pharmacology , Pyrrolidines/antagonists & inhibitors , Pyrrolidines/metabolism , Tandem Mass Spectrometry/methods , ZolpidemABSTRACT
OBJECTIVE: The aim of the present study was to estimate the drug interaction potential of psychtropic medication on buprenorphine (BUP) N-dealkylation using cDNA-expressed cytochrome P450 (CYP) enzymes. METHODS: BUP was incubated with psychotropic drugs and cDNA-expressed CYP 3A4 and CYP 2C8 enzymes. Seven substances were screened for their inhibition potency. To check for a mechanism-based component in inhibition, all substances were tested with and without preincubation, respectively. Norbuprenorphine (NBUP) concentrations were determined by liquid chromatography/tandem mass spectrometry, following liquid/liquid extraction. RESULTS: Midazolam and zolpidem demonstrated greatest inhibition in screening experiments. As expected, IC(50) values without preincubation were higher than those after 30-min preincubation, with zolpidem 113.1 microM and midazolam 20.25 microM. Following a 30-min preincubation period in the absence of the probe substrate BUP, the apparent IC(50) values for zolpidem and midazolam were 20.17 microM and 3.5 microM. CONCLUSION: Both midazolam and zolpidem showed a distinct inhibitory potency towards NBUP formation by CYP 3A4, implicating a decreased conversion of BUP. When preincubated, the inhibitory potency was increased, which strongly suggests a metabolically activated component in inhibition.
