SENSITIVE, HIGH-THROUGHPUT AND ENANTIOSELECTIVE QUANTITATION OF ZOPICLONE IN HUMAN PLASMA BY LCMS/MS: APPLICATION TO A HUMAN PHARMACOKINETIC STUDY

Zopiclone (ZPC), a cyclopyrrolone derivative, is a short-acting hypnotic agent. Its pharmacological properties include hypnotic, sedative, anxiolytic, anticonvulsant and muscle-relaxant actions. ZPC has a single chiral centre, and its enantiomers are S-zopiclone (S-ZPC) and R-zopiclone (R-ZPC). S-ZPC was adjudge to possess two- fold enhanced pharmacological activity than racemate (ZPC) while its opposite enantiomer R-ZPC appears to have almost zero activity and elevated toxicity. A high performance LC-MS\MS method employing positive electrospray ionization was developed for the simultaneous determination of both S-ZPC and R-ZPC in human plasma samples by using S-Zopiclone d8 as internal standard. Analytes were extracted from plasma samples by employing solid phase extraction technique. After extraction, 5µL of clean sample was injected on to chromatographic system and distinct separation achieved on chiralpak IC-3, 0.46 cm I.D*15 cm L column with the isocratic mobile phase consisting of a mixture of Ammonia in Acetonitrile and Milli Q Water. Detection was performed using API 4000 MS that monitors specific transition per compound in Multi Reaction monitoring mode. Limit of quantitation achived is 0.500ng/mL. The developed method is validated as per USFDA guidelines and used for quantifying S-ZPC and R-ZPC in human plasma and has been successfully applied to a pharmacokinetic study