EFFECT OF pH ON THE PHOTOSTABILITY OF SULPHACETAMIDE EYE-DROP SOLUTIONS.

The photolysis of aqueous solutions of sulphacetamide and sulphanilamide has been studied at pH 3-11. The rate of phatolysis appears to be the highest around pH 5.0 and 3.0 for sulphacetamide and sulphanilamide respectively. The log k-pH profiles of both compounds in the buffered and unbuffered solutions are presented. Various buffer ions e.g. citrate and phosphate catalyase the photodegradation reactions. Sulphacetamide eye-drop solutions prepared at pH 7 to 9 have ideal stability and clinical efficacy.