STUDIES ON SOME FACTORS AFFECTING THE STABILITY OF RIFAMPICIN IN SOLUTION

Rifampicin stability in relation to a number of factors namely; solvent type, pH value, type of buffering system, ionic strength and storage temperature was investigated. Kinetic treatment of the obtained data revealed first order pattern for rifampicin degradation. The degradation rate constant varied according to the type of the solvent, the pH of the solution, the type of the buffering components, the ionic strength and the storage temperature. Degradation was accelerated in solvents of higher dielectric constants in contrast to those of lower dielectric constants. The pH for minimal degradation was found to be pH 6. Rifampicin degradation proceeded at minimal rate in presence of ascorbate buffer compared to formate, acetate, phosphate, Sorensens phosphate and Mcilvaine's citric acid-phosphate buffering systems. The calculated activation energy (Ea) and frequency factors of rifampicin was 15.47 K. cal/mol and 2.16 x 109 day-1 respectively.