Microbiological assay for terbinafine hydrochloride in tablets and creams

The optimization of a microbiological assay, applying the cylinder-plate method, for the determination of the antifungal terbinafine hydrochloride is described. Using a strain of Aspergillus flavus ATCC 15546 as the test organism, terbinafine hydrochloride at concentrations ranging from 0.125 to 0.5 microg ml(-1) could be measured in tablets and creams. A prospective validation of the method showed that the method was linear (r=0. 9999), precise (intra-day: CV=0.48%-tablets and 0.43%-creams; inter-day: CV=0.98%-tablets and 0.64%-creams) and accurate (it measured the added quantities). The method shows results that confirm its precision, not differing significantly the others methods described in the literature. We conclude that the microbiological assay is satisfactory for quantitation of in vitro antifungal activity of terbinafine.