Corticosteroid determination in skin preparations by a reaction rate method.

A reaction rate method for the determination of beta-methasone, betamethasone valerate, triamcinolone acetonide, and fluocinolone acetonide is described. The method is based on a modification of the widely accepted blue tetrazolium reaction. Analysis times of 30--70 sec are required. Relative standard deviations of 0.3--1.9% are obtained, and the analytical working curves are linear. Analysis of pharmaceutical skin preparations by the new method gave results that correlated well with the time-consuming standard equilibrium method. Analysis of betamethasone and betamethasone valerate mixtures by measuring absorbance values at two different times was performed also.