Biopharmaceutic and pharmacokinetic aspects of variable bioavailability of rifampicin.

Even today the treatment outcome of tuberculosis is questionable due to variable bioavailability of rifampicin, which was discovered four decades back. In this manuscript, results of bioequivalence trials reported are presented in the form of a figure that provides a comprehensive look at the rifampicin bioavailability literature, provides understanding of the problem and clears 'myths and assumptions' regarding rifampicin bioavailability from fixed-dose combination (FDC) formulations. It was found that FDCs of good as well as bad quality rifampicin containing formulations with reduced or increased relative bioavailability are available. In addition, 'rifampicin alone' formulations also show variability in bioavailability. In the context of anomalous bioavailability of rifampicin, reasons postulated in literature are summarized. Approaches needed to solve the issue of rifampicin bioavailability are discussed on the basis of LADMER and BCS.