Impact of Cytochrome P450 2D6 Function on the Chiral Blood Plasma Pharmacokinetics of 3,4-Methylenedioxymethamphetamine (MDMA) and Its Phase I and II Metabolites in Humans.

3,4-methylenedioxymethamphetamine (MDMA; ecstasy) metabolism is known to be stereoselective, with preference for S-stereoisomers. Its major metabolic step involves CYP2D6-catalyzed demethylenation to 3,4-dihydroxymethamphetamine (DHMA), followed by methylation and conjugation. Alterations in CYP2D6 genotype and/or phenotype have been associated with higher toxicity. Therefore, the impact of CYP2D6 function on the plasma pharmacokinetics of MDMA and its phase I and II metabolites was tested by comparing extensive metabolizers (EMs), intermediate metabolizers (IMs), and EMs that were pretreated with bupropion as a metabolic inhibitor in a controlled MDMA administration study. Blood plasma samples were collected from 16 healthy participants (13 EMs and three IMs) up to 24 h after MDMA administration in a double-blind, placebo-controlled, four-period, cross-over design, with subjects receiving 1 week placebo or bupropion pretreatment followed by a single placebo or MDMA (125 mg) dose. Bupropion pretreatment increased the maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from 0 to 24 h (AUC24) of R-MDMA (9% and 25%, respectively) and S-MDMA (16% and 38%, respectively). Bupropion reduced the Cmax and AUC24 of the CYP2D6-dependently formed metabolite stereoisomers of DHMA 3-sulfate, DHMA 4-sulfate, and 4-hydroxy-3-methoxymethamphetamine (HMMA sulfate and HMMA glucuronide) by approximately 40%. The changes that were observed in IMs were generally comparable to bupropion-pretreated EMs. Although changes in stereoselectivity based on CYP2D6 activity were observed, these likely have low clinical relevance. Bupropion and hydroxybupropion stereoisomer pharmacokinetics were unaltered by MDMA co-administration. The present data might aid further interpretations of toxicity based on CYP2D6-dependent MDMA metabolism.

Chiral Plasma Pharmacokinetics of 3,4-Methylenedioxymethamphetamine and its Phase I and II Metabolites following Controlled Administration to Humans.

Generally, pharmacokinetic studies on 3,4-methylenedioxymethamphetamine (MDMA) in blood have been performed after conjugate cleavage, without taking into account that phase II metabolites represent distinct chemical entities with their own effects and stereoselective pharmacokinetics. The aim of the present study was to stereoselectively investigate the pharmacokinetics of intact glucuronide and sulfate metabolites of MDMA in blood plasma after a controlled single MDMA dose. Plasma samples from 16 healthy participants receiving 125 mg of MDMA orally in a controlled study were analyzed using liquid chromatography-tandem mass spectroscopy after chiral derivatization. Pharmacokinetic parameters of R- and S-stereoisomers were determined. Sulfates of 3,4-dihydroxymethamphetamine (DHMA), and sulfate and glucuronide of 4-hydroxy-3-methoxymethamphetamine (HMMA) were identified, whereas free phase I metabolites were not detected. Stereoselective differences in Cmax and AUC24 were observed with the following preferences: R>S for MDMA and DHMA 4-sulfate; S>R for 3,4-methylenedioxyamphetamine (MDA), DHMA 3-sulfate, and HMMA glucuronide; and no preference in Cmax for HMMA sulfate. R/S ratios were >1 for all analytes after 24 hours, independent of the initial chiral preference. These are the first data on chiral pharmacokinetics of MDMA phase II metabolites in human plasma in vivo after controlled administration. The main human MDMA metabolites were shown to be sulfate and glucuronide conjugates.

Development and validation of an LC-MS/MS method after chiral derivatization for the simultaneous stereoselective determination of methylenedioxy-methamphetamine (MDMA) and its phase I and II metabolites in human blood plasma.

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is a racemic drug of abuse and its two enantiomers are known to differ in their dose-response curves. The S-enantiomer was shown to be eliminated at a higher rate than the R-enantiomer. The most likely explanation for this is a stereoselective metabolism also claimed in in vitro studies. Urinary excretion studies showed that the main metabolites in humans are 4-hydroxy 3-methoxymethamphetamine (HMMA) 4-sulfate, HMMA 4-glucuronide and 3,4-dihydroxymethamphetamine (DHMA) 3-sulfate. For stereoselective pharmacokinetic analysis of phase I and phase II metabolites in human blood plasma useful analytical methods are needed. Therefore the aim of the presented study was the development and validation of a stereoselective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of MDMA, 3,4-methylenedioxyamphetamine, DHMA, DHMA 3-sulfate, HMMA, HMMA 4-glucuronide, HMMA 4-sulfate, and 4-hydroxy 3-methoxyamphetamine in blood plasma for evaluation of the stereoselective pharmacokinetics in humans. Blood plasma samples were prepared by simple protein precipitation and afterwards all analytes were derivatized using N-(2,4-dinitro-5-fluorophenyl) L-valinamide resulting in the formation of diastereomers which were easily separable on standard reverse phase stationary phases. This simple and fast method was validated according to international guidelines including specificity, recovery, matrix effects, accuracy and precision, stabilities, and limits of quantification. The method proved to be selective, sensitive, accurate and precise for all tested analytes except for DHMA.