P450 phenotyping of the metabolism of selegiline to desmethylselegiline and methamphetamine

Although there is evidence in the literature of the participation of CYP2B6 in the metabolism of selegiline, it is not clear which other CYP isofoms contribute to its metabolism. The aim of this study was to investigate the P450 isozymes (CYPs) involved in the metabolism of selegiline to desmethylselegiline (DMS) and methamphetamine (MA) using four assays: incubation of selegiline with cDNA expressed CYPs, inhibition of DMS and MA formations in human liver microsomes by CYP-selective chemical inhibitors or CYP-specific antibodies, and correlation analysis. Correlation analysis, performed in a bank of 15 individual human liver microsomes, yielded correlation coefficients for DMS and MA formation of 0.769 and 0.792, respectively, for CYP2136 (p < 0.0001) and 0.333 and 0.349, respectively, for CYP3A4 (p < 0.05). These results were supported by chemical /specific antibody inhibition assays. The results of correlation analysis and chemical inhibition also indicated that CYP2A6 seems to play a small role in the metabolism of selegiline. These findings confirm that CYP2136 plays a major role in the metabolism of selegiline and also suggest the involvement of CYP3A4 and CYP2A6.