Identification of monoamine oxidase and cytochrome P450 isoenzymes involved in the deamination of phenethylamine-derived designer drugs (2C-series).

For several phenethylamine-type designer drugs (2C-series), the main metabolic step is deamination to an aldehyde. Using human enzymes expressed in cell culture, monoamine oxidase A and B (MAO-A and MAO-B) were the primary catalysts of this reaction for all compounds tested. For four of the six drugs (2C-D, 2C-E, 2C-T-2, and 2C-T-7), the cytochrome P450 enzyme CYP2D6 contributed to a very small extent. Because MAO enzymes are the major route of metabolism, these designer drugs are likely to be susceptible to drug-drug interactions with MAO inhibitors.

Study at a glance

Abstract

In recent years, several compounds of the phenethylamine-type (2C-series) have entered the illicit drug market as designer drugs. In former studies, the qualitative metabolism of frequently abused 2Cs (2C-B, 2C-I, 2C-D, 2C-E, 2C-T-2, 2C-T-7) was studied using a rat model. Major phase I metabolic steps were deamination and O-demethylation. Deamination to the corresponding aldehyde was the reaction, which was observed for all studied compounds. Such reactions could in principal be catalyzed by two enzyme systems: monoamine oxidase (MAO) and cytochrome P450 (CYP). The aim of this study was to determine the human MAO and CYP isoenzymes involved in this major metabolic step and to measure the Michaelis-Menten kinetics of the deamination reactions. For these studies, cDNA-expressed CYPs and MAOs were used. The formation of the aldehyde metabolite was measured using GC-MS after extraction. For all compounds studied, MAO-A and MAO-B were the major enzymes involved in the deamination. For 2C-D, 2C-E, 2C-T-2 and 2C-T-7, CYP2D6 was also involved, but only to a very small extent. Because of the isoenzymes involved, the 2Cs are likely to be susceptible for drug-drug interactions with MAO inhibitors.