Simultaneous determination of ornidazole and its main metabolites in human plasma by LC-MS/MS: application to a pharmacokinetic study

Background: Ornidazole is a 5-nitroimidazole antimicrobial agent used for almost 40 years. A novel LC-MS/MS assay was developed and validated for the simultaneous determination of ornidazole and its main metabolites (M3, M6, M16-1, and M16-2) in human plasma. Results: After extraction from 100 l of plasma by protein precipitation with acetonitrile, all the analytes were separated on a Capcell PAK MG C-18 column (100 x 4.6 mm, 5 m) within 5.0 min and detected by ESI-MS/MS in the positive mode. The validation results met the acceptance criteria as per the US FDA and EMA guidelines. Conclusion: The validated method was successfully applied to a pharmacokinetic study after oral administration of 1000 mg ornidazole to six healthy Chinese volunteers.