Concern has been expressed about the bioavailability of rifampicin in some fixed-dose combination (FDC) anti-tuberculosis formulations.
To evaluate the relative bioavailability of rifampicin in various FDC formulations currently in use in tuberculosis control programmes in the global market.
A two-period randomised crossover bioequivalence study in healthy male volunteers, with a 1 week washout period between treatments. Plasma rifampicin concentrations were measured at 0, 1, 2, 4, 6, 8 and 12 hours after each drug administration.
The AUC0-8, AUC0-12 and Cmax for rifampicin in seven of 10 FDC formulations was not found to be bioequivalent to the reference administered as loose (separate) formulations. This was confirmed using parametric and non-parametric statistical methods.
The poor relative bioavailability of rifampicin from some FDCs has been documented. The implications for tuberculosis programmes are extremely serious and warrant urgent attention.