Determination of sodium fusidate and fusidic acid in dosage forms by high-performance liquid chromatography and a microbiological method.

A new High-performance liquid chromatographic (HPLC) method for the assay of sodium fusidate (I) or fusidic acid in dosage forms was developed and compared to a microbiological assay. A linear relationship was obtained between absolute peak area and amount of I(r = 0.99+) in the 50-1000-microgram/ml range. In the microbiological assay, Staphylococcus aureus (NCTC 6571) was the test organism, using an agar diffusion technique. With five test levels of the standard, potencies were interpolated from standard curve using a log transformation straight-line method with least-squares fitting (r = 0.99+). Both methods were applied to assay I (or fusidic acid) in tablets, a suspension, and an ointment. Excellent agreement was observed between results of the two methods.