Development and validation of a stability indicating method for S-carboxymethyl-L-cysteine and related degradation products in oral syrup formulation.

A stability-indicating method for the determination of S-carboxymethyl-L-cysteine and related degradation impurities in Exputex® 250mg/5mL syrup was developed in anion-exchange liquid chromatography mode. A forced degradation study supported the method development to ensure stability indicating conditions. Aqueous solutions of the active pharmaceutical ingredient and syrup samples at different pH-values were stress-tested in different thermal, light exposure and headspace conditions.