Analysis of betamethasone and its organic esters in pharmaceutical products.

A rapid, quantitative analysis for betamethasone and its organic esters at room temperature is described. The method is similar to the official blue tetrazolium reaction for corticosteroids, except that methylene chloride is used as the solvent. The reaction is complete in 27-69 min, and the formazans produced are stable for at least 90 min after the addition of tetramethylammonium hydroxide. The results of the analysis of 13 different pharmaceutical formulations by the proposed method are reported. The degradation of betamethasone and its esters caused by strong bases is a pseudo-first-order reaction in methylene chloride. The average half-life of the corticosteroids studied is 56 min under the basic conditions described.