Photostability Issues in Pharmaceutical Dosage Forms and Photostabilization

Photodegradation is one of the major pathways of the degradation of drugs. Some therapeutic agents and excipients are highly sensitive to light and undergo significant degradation, challenging the quality and the stability of the final product. The adequate knowledge of photodegradation mechanisms and kinetics of photosensitive therapeutic entities or excipients is a pivotal aspect in the product development phase. Hence, various pharmaceutical regulatory agencies, across the world, mandated the industries to assess the photodegradation of pharmaceutical products from manufacturing stage till storage, as per the guidelines given in the International Conference on Harmonization (ICH). Recently, numerous formulation and/or manufacturing strategies has been investigated for preventing the photodegradation and enhancing the photostability of photolabile components in the pharmaceutical dosage forms. The primary focus of this review is to discuss various photodegradation mechanisms, rate kinetics, and the factors that influence the rate of photodegradation. We also discuss light-induced degradation of photosensitive lipids and polymers. We conclude with a brief note on different approaches to improve the photostability of photosensitive products.