Comparative bioavailability and in-vitro antimicrobial activity of two different brands of rifampicin

A comparative bioavailability study was undertaken between a new formulation of rifampicin 'Famcin' and a standard formulation of rifampicin 'R-cin' in eight healthy male volunteers at two dose levels: 300 mg and 450 mg given orally under both single dose and steady state conditions. Plasma rifampicin was assayed spectrophotometrically. The study documented comparable rate and extent of bioavailability. (Cmax, Tmax and AUC0-infinity) and elimination half-lives (t1/2) of the two brands of rifampicin when compared at similar dose levels. The study establishes the bioequivalence of Famcin to that of the standard brand R-cin. Further, a comparative in vitro microbiological sensitivity of the two brands of rifampicin was undertaken against several strains of two test micro-organism viz. Staphylococcus aureus and Mycobacterium tuberculosis. For both the micro-organisms the minimal inhibitory concentration of Famcin was lower than that of R-cin, suggesting a somewhat greater potency of Famcin in suppressing the growth of test micro-organisms.