Pharmacokinetics and Bioequivalence of Sitagliptin Phosphate/Metformin Hydrochloride Tablets in Healthy Chinese Subjects: A Randomized, Open-Label, Crossover Study

OBJECTIVE: Our objective was to evaluate the pharmacokinetics and bioequivalence of test and reference (JANUMET(®)) formulations of sitagliptin phosphate/metformin hydrochloride tablets at a single dose of 50 mg/850 mg. METHODS: The study was a randomized, open-label, two-period, double-crossover trial. Volunteers under fasting (n = 24) and fed (n = 24) conditions were given a single oral dose of test or reference formulations of sitagliptin phosphate/metformin hydrochloride tablets 50 mg/850 mg. We used the liquid chromatography tandem mass spectrometry method to determine the concentrations of sitagliptin and metformin in the plasma of subjects. Pharmacokinetic metrics were calculated using the WinNonlin 7.0 program, and bioequivalence was evaluated using SAS 9.4. RESULTS: Under the fasting condition, the 90% confidence intervals (CIs) of geometric mean ratio for maximum plasma drug concentration (C(max)), area under the plasma concentration–time curve from time zero to time t (AUC(0–t)), and AUC from time zero to infinity (AUC(0–∞)) of sitagliptin between the test and reference groups were 101.70–120.62%, 99.81–105.61%, and 100.27–106.12%, respectively; for metformin, they were 90.39–111.48%, 94.76–109.12%, and 95.76–110.38%, respectively. Under the fed condition, they were 102.12–117.31%, 100.80–107.81%, and 100.82–107.78%, respectively, for sitagliptin and 95.53–105.22%, 92.76–103.07%, and 93.40–104.14%, respectively, for metformin. Both were generally well-tolerated. CONCLUSION: The two formulations of sitagliptin phosphate/metformin hydrochloride tablets were bioequivalent under fasting and fed conditions in healthy Chinese subjects.