In vivo phenotyping of cytochrome 450 isoforms involved in the metabolism of anti-HIV and anti-tubercular drugs in human using cocktail approach: An LC-MS/MS analysis

Abstract

Purpose: In vivo phenotyping of CYP isoforms involved in the metabolism of anti-HIV and antitubercular drugs is important to determine therapeutic dose levels in HIV/AIDS-TB coinfections. In this study, we used a cocktail of bupropion, losartan and dapsone for in vivo phenotyping of CYP2B6, CYP2C9 and N-acetyltransferase-2 (NAT2) in plasma. CYP2B6 is the main catalyst of anti-HIV efavirenz, while NAT2 is involved in antitubercular drug isoniazid metabolism. CYP2C9 has a significant association with antitubercular drug-induced reactions. The activity level of these isoforms has a significant bearing on therapeutic dose in rapid and poor metabolizers.

Methods: Briefly, a cocktail of probe drugs was administered to human volunteers and the drugs and metabolites were determined by an inhouse LC-MS/MS method in 250 μl plasma. The mobile phase and drug/metabolite extraction methods were optimized before analysis. Retention time, Cmax and tmax were calculated from the same sample and the values were used for phenotyping the isoforms.

Results: Retention time of drugs and metabolites was calculated. The method was sensitive (4.5-8.2 %CV) and no interfering peak was observed in any batch. %Accuracy of the calibrator and QC was 85-115%. %CV of storage stability testing was within FDA approved limits. Cmax and tmax were comparable to the values reported for individual drugs.

Conclusions: This study advocates the use of a cocktail of bupropion, losartan and dapsone for in vivo phenotyping of CYP2B6, CYP2C9 and NAT2, which is important in determining therapeutic dose levels of anti-HIV and anti-TB drugs in HIV/AIDS-TB coinfections.

Keywords: Antitubercular; Bupropion; CYP2B6; CYP2C9; Dapsone; Drug metabolism; HIV AIDS; Losartan; NAT2.