Setting: The benefits of fixed-dose combination (FDC) formulations of rifampicin, isoniazid and pyrazinamide over individual formulations are well recognised.
Objectives: To evaluate the comparative bioavailability of antituberculosis drugs in FDC formulations and the same doses in separate formulations of antituberculosis drugs, using a simplified protocol developed by the World Health Organization (WHO).
Methods: Twenty healthy volunteers were included in the study and evaluated for bioequivalence of rifampicin in a cross-over experimental design. After administration of drugs the plasma concentration of rifampicin and desacetyl-rifampicin was measured repeatedly up to 8 hours in both plasma and urine. Various pharmacokinetic parameters of rifampicin, such as Cmax, Tmax, elimination rate constant, area under the curve (AUC) up to 8 hours and absorption efficiency were calculated.
Results: No significant differences were observed between the FDCs and separate formulations when Cmax, Tmax, AUC and absorption efficiencies were compared by parametric test and Hauschke's analysis.
Conclusion: The WHO simplified protocol is suitable for evaluating bioequivalence of antituberculosis drugs.