Simple high-performance liquid chromatographic separation of oxazepam and its diastereoisomeric glucuronides in serum - Applications in a pharmacokinetic study in sheep

This paper describes a highly specific and sensitive method for quantifying oxazepam and its diastereoisomeric glucuronides in serum. The method involves sample clean-up by solid-phase extraction on C-18 cartridge followed by quantitation on a reversed-phase HPLC column. Diazepam is used as internal standard. Extraction recovery from serum proved to be more than 86%. Precision, expressed as C.V., was in the range 1.2-9.5%. The limits of quantification were 40, 400, and 200 nmol/l for oxazepam, S-(+)- and R-(-)-glucuronides, respectively. This method was applied to the determination of oxazepam and its diastereoisomeric glucuronides in serum collected during a pharmacokinetic study performed in sheep after oral administration of racemic oxazepam. S-(+)/R-(-) ratios were measured all along the sampling time collection and the pharmacokinetic parameters were determined.