Comparative bioavailability and pharmacokinetics of sirolimus tablets in healthy Chinese volunteers

Objectives: Although sirolimus tablets and oral solutions have been used in clinical practice, no study has been reported on the pharmacokinetics and bioavailability of a single-dose of sirolimus tablets in healthy Chinese volunteers. The purpose of this study was to compare the bioavailability and pharmacokinetic (PK) properties of two different 1-mg sirolimus tablets in healthy Chinese male volunteers and evaluate whether a generic tablet of sirolimus meets the criteria for bioequivalence from the State Food and Drug Administration (SFDA) of China when compared with a reference product. Materials and methods: A total of 24 healthy Chinese volunteers was eligible for this 6 mg single-dose, randomized-sequence, open-label, 2-period crossover study. Blood samples were collected before dosing and at 0.25, 0.50, 0.75, 1.0, 1.5, 2, 3, 4, 8, 12, 24, 48, 72, 120, 168, 216, and 264 hours after dosing. Whole blood sirolimus concentration was analyzed by a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Pharmacokinetic properties of sirolimus were assessed using noncompartmental analysis. Results: The mean (range) C-max values of the test and the reference were 15.25 (8.48 - 24.40) and 13.43 (7.90 - 22.90) ng/ml; AUC(0-t) values were 475.65 (293.33 - 1049.86) and 451.96 (221.52 - 809.11) ng/h/ml. The medians (range) t(max) values were 2.0 (1.0 - 8.0) and 2.0 (1.0 - 8.0) hours, respectively. The 90% confidence intervals (CIs) for the ratios of C-max AUC(0-264), and AUC(0-infinity) were 103.7 - 124.4%, 97.5 - 113.6%, and 98.0 - 114.8%, respectively. Conclusion: In this single-dose crossover study the test sirolimus tablets met the criteria for bioequivalence in terms of both rate and extent. Each sirolimus formulation was well tolerated during the study.