Objective: To study the relative bioavailabilities of two generic rifampicin preparations with Rimactane.
Method: Each of nineteen healthy volunteers received a single oral dose of 600 mg of rifampicin in an open cross-over randomised three-way single-dose design with a washout period of 7 days between each doses. Plasma concentrations of rifampicin were determined by HPLC. In vitro dissolution profiles of the same drugs were determined and compared with human bioavailability study results.
Results: No statistically significant difference was found in main bioavailability parameters between Rimactane and generic preparations studied. Both generic preparations also fulfilled the bioequivalence criteria based on the 90% confidence intervals. There was a good correlation between in vivo and in vitro results: faster dissolution time corresponded to the lower Tmax value; lower percentage of released compound to the lower AUC value. Significant intersubject variations were found in main bioavailability parameters; significant negative correlation was found between average AUC values and body weight of the volunteer.
Conclusion: All three products were bioequivalent. Our results also suggest the suitability of one-compartmental model with lag time, first order input and first order output to describe the kinetics of rifampicin.