The formulation and stability of erythromycin benzoyl peroxide in a topical gel

The combination of benzoyl peroxide and erythromycin is used for the local treatment of acne and available as a commercial preparation. Because of the stability problems of erythromycin an extempore preparation is required. T he influence of storage temperature and non active ingredients on the stabi lity of benzoyl peroxide and erythromycin in topical gel preparations for e xtempore compounding is described. A microbiological and an HPLC method wer e used to determine the erythromycin and the benzoyl peroxide concentration s, respectively. For a formulation compounded with hydroxyethylcellulose no stability problems were observed. For the formulation containing Carbopol 940(R), the levels of erythromycin varied over a wide range due to precipit ation and aggregation of the drug during compounding. (C) 1999 Elsevier Sci ence B.V. All rights reserved.