Bioequivalence study of rifampicin in fixed-dose combination of rifampicin and isoniazid vs. separate formulations.

The benefits of fixed-dose combinations of antituberculosis agents are well recognized by the World Health Organization (WHO) and International Union Against Tuberculosis and Lung Disease (IUATLD) and preferred over separate formulations. Therefore, a comparative bioequivalence study of rifampicin and isoniazid together in a fixed-dose combination and separately (at the same dose levels) was performed on a group of 12 healthy subjects. The study was designed as a single-blind, crossover experiment. Nine blood samples were collected from each subject over a period of 24 h. The plasma concentrations of rifampicin were assessed by a method developed in this laboratory. Various pharmacokinetic parameters of rifampicin such as AUC, Cmax, Tmax and t1/2 were also calculated. The study demonstrates that a fixed-dose combination (test formulation) and separate formulations (standard formulations) are bioequivalent for rifampicin.