Tashtoush Bassam M, Jacobson Elaine L, Jacobson Myron K
Department of Pharmaceutical Technology, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan.
Int J Pharm. 2008 Mar 20;352(1-2):123-8. doi: 10.1016/j.ijpharm.2007.10.045. Epub 2007 Nov 4.
The chemical stability of tretinoin (RA) and isotretinoin (13RA) in ethanol and dermatological cream preparations exposed to solar simulated light (SSL), UVA, and visible light has been studied. Photostability was monitored by an HPLC method that allowed simultaneous analysis of RA and 13RA, thus allowing photodegradation due to isomerization to other retinoids and photolysis to non-retinoid products to be monitored. Both retinoids undergo both isomerization and photolysis following SSL, UVA and visible light exposure but RA is more sensitive to photodegradation than 13RA. Degradation of both retinoids by photolysis is considerably greater in cream formulations than in ethanol and the photodegradation follows second order kinetics. Rate constants and half-lives for degradation of RA and 13RA in ethanol solution and cream preparations subjected to different light sources are reported. The UVA component of SSL is the major contributor to photodegradation. Since UVA penetrates deeply into skin, our results suggest that photodegradation of RA may contribute to the photosensitivity associated with RA therapy. Our studies suggest that development of improved formulations and the use of effective UVA sunscreens may reduce the side effects of RA therapy.
已对维甲酸（RA）和异维甲酸（13RA）在乙醇以及暴露于模拟太阳光（SSL）、UVA和可见光下的皮肤科乳膏制剂中的化学稳定性进行了研究。通过一种HPLC方法监测光稳定性，该方法能够同时分析RA和13RA，从而可以监测由于异构化为其他类视黄醇以及光解为非类视黄醇产物而导致的光降解。在暴露于SSL、UVA和可见光后，两种类视黄醇都会发生异构化和光解，但RA比13RA对光降解更敏感。在乳膏制剂中，两种类视黄醇的光解降解程度比在乙醇中要大得多，并且光降解遵循二级动力学。报告了RA和13RA在乙醇溶液以及经受不同光源的乳膏制剂中的降解速率常数和半衰期。SSL中的UVA成分是光降解的主要贡献因素。由于UVA能深入皮肤，我们的结果表明RA的光降解可能导致与RA治疗相关的光敏性。我们的研究表明，开发改进的制剂以及使用有效的UVA防晒剂可能会减少RA治疗的副作用。
