The role of human hepatic cytochrome P450 isozymes in the metabolism of racemic 3,4-methylenedioxyethylamphetamine and its single enantiomers.

The 3,4-methylenedioxy-methamphetamine (MDMA)-related designer drug 3,4-methylenedioxyethylamphetamine (MDEA, Eve) is a chiral compound that is mainly metabolized by N-deethylation and demethylenation during phase I metabolism. The involvement of several cytochrome P450 (P450) isozymes in these metabolic steps has been demonstrated by inhibition assays using human liver microsomes. However, a comprehensive study on the involvement of all relevant human P450s has not been published yet. In addition, the chirality of this drug was not considered in these in vitro studies. The aim of the present work was first to elucidate the contribution of the relevant human P450 isozymes in the demethylenation as well as in the N-dealkylation of racemic MDEA and its single enantiomers and secondly to compare these findings with recently published data concerning the enantioselective metabolism of MDMA. Racemic MDEA and its single enantiomers were incubated using heterologously expressed human P450s, and the corresponding metabolites dihydroxyethylamphetamine and methylenedioxyamphetamine were determined by gas chromatography-mass spectrometry after chiral derivatization with S-heptafluorobutyrylprolyl chloride. The highest contributions to both metabolic steps as calculated from the enzyme kinetic data were obtained for CYP3A4 and CYP2D6 at substrate concentrations corresponding to plasma concentrations of recreational users after intake of racemic MDEA. Both metabolic reactions were found to be enantioselective with a general preference for the S-enantiomers, which was particularly pronounced in the case of CYP2C19. In conclusion, different pharmacokinetic properties of MDEA enantiomers observed in vivo are therefore partially caused by P450-dependent enantioselective metabolism.