Rapid determination of loxoprofen in human plasma by HPLC-MS and its pharmacokinetics and bioequivalence study

AIM: To develop an assay for the quantification of the loxoprofen in human plasma and study its pharmacokinetics and bioequivalence in healthy volunteers.METHODS: The method involves the addition of ibuprofen(internal standard) solution in methanol,hexane-ether(41,v/v) solution to(0.2) ml acidified plasma sample,followed by centrifugation.Separations were performed on Diamonsil 150 mm×(2.1) mm,5 μm column with the mobile phase of(0.2)% NH_4 Ac-acetonitrile(2575,v/v).This LC-MS method was established for the determination of loxoprofen in human plasma after a single oral dose administration of 60 mg loxoprofen sodium(test preparation and reference preparation) in a crossover design.RESULTS: The method is successfully validated in the pharmacokinetics study of loxoprofen in human volunteers.The main pharmacokinetic parameters after a single dose administration of 60 mg loxoprofen sodium were as follows(test and reference):C_(max)(7.17)±(1.63) and(6.94)±(13.30)(μg·ml~(-1)),T_(max)(0.46)±(0.23) and(0.46)±(0.28) h,AUC_(0-10)(11.65)±(13.75) and(11.19)±(18.28)(μg·ml~(-1)·h),AUC_(0-∞)(12.04)±(1.42) and(11.64)±(1.89)(μg·ml~(-1)·h).CONCLUSION: The method is simple and readily applicable to routine bioavailability studies of loxoprofen sodium with high sensitivity and the relative bioavailability of loxoprofen sodium is((105.3)±(11.5))%.The results show that the test and reference preparation are bioequivalent.