Stability of hydrophilic gels of tretinoin

Abstract Tretinoin is the trans isomeric form of retinoic acid. Its chemical structure includes a functional acid group and a side chain with conjugated double bonds, both susceptible to redox reactions. The vitamin C redox system comprises l -ascorbic acid, monodehydroascorbic acid and dehydroascorbic acid. Each of these substances has different physicochemical properties but possess antioxidant capacity for both hydrophilic and lipophilic substances. The present work is centred on studying the stability of hydrophilic gels of tretinoin prepared with or without antioxidant. HPLC was used to validate the analytical and extraction techniques to determine the amounts of tretinoin remaining. The results indicate that tretinoin undergoes rapid degradation by oxidation of the conjugated double bonds which is neither retarded nor lessened by the presence of antioxidant.