Predicting drug interaction of diltiazem on microbial metabolism of midazolam

The present investigation was aimed at studying the biotransformation of midazolam, a marker substrate for CYP3A4 metabolic reactions using nine microbial cultures. The study was performed using a two stage fermentation protocol and the results indicate that the microbial cultures produce hydroxylated metabolites of midazolam, based on HPLC-DAD and LC-MS-MS analysis. The metabolism of midazolam was also studied in presence of diltiazem, a CYP3A4 specific inhibitor in order to elucidate the nature of enzymes involved in the biotransformation. The results of the inhibition study reveal that diltiazem produced a concentration dependent inhibition of midazolam metabolism in four cultures indicating that the enzymes participating in the metabolism in these cultures were similar to that of CYP3A4. The results indicate that microbial cultures possess enzyme systems similar to mammals and they can be used to predict drug interactions in mammalian systems. The study will be helpful in developing models for simulation of mammalian drug metabolism and drug interactions. This will greatly reduce the number of animals used in early stages of drug development.