Bioavailability of medroxyprogesterone acetate from three oral dosage formulations

The bioavailability of three formulations of medroxyprogesterone acetate (MPA) was assessed in 30 healthy male volunteers in a three-way, open-label, cross-over-designed trial. Each subject received one Provera 500-mg tablet, one Farlutal 500-mg tablet, and one Provera 500-mg granule packet according to a randomized schedule, with each treatment separated by a 21-day washout period. Serum MPA levels were determined using both radioimmunoassay (RIA) and high-performance liquid chromatography techniques. Based on the results of RIA analysis, Farlutal tablets produced significantly lower serum MPA concentrations compared with Provera tablets at most sampling times, resulting in statistically lower AUC0-144 for the Farlutal tablet (544 vs 768 ng.hr/ml; -29.2%). The Farlutal tablet also had a significantly lower maximum concentration than the Provera tablet (27.8 vs 47.4 ng/ml; -41.4%). However, there was no significant difference in time of maximum concentration between the tablet formulations (3.71 vs 3.41 hr), indicating that the rates of absorption of the two tablet formulations were comparable. Provera granules provided significantly higher serum MPA levels than Provera tablets at 0.5, 1, 1.5, 2, and 6 hours, and the AUC0-144 for Provera granules was higher by 5.47% (810 vs 768 ng.hr/ml). There were no differences in terminal elimination rate constants among the dosage forms. No significant adverse events were noted during the trial. The relative bioavailabilities of Provera granules and Farlutal tablets were 105% and 71.2%, respectively, compared with Provera tablets.