Photostability stress testing

The problem of photostability of drugs has received relatively little attention in the pharmaceutical industry. In 1998, the implementation of the ICH guidelines as to how carry out photostability tests on new pharmaceutical drug substances and drug products introduced a reference point. The guideline refers to 'confirmatory' testing, where a fixed light dose impinges on the sample. It also hints to the possibility of carrying out 'stress' testing. It should establish photodegradation pathways and allow identification of degradation products in order to validate the fitness of the analytical procedures used for confirmatory studies. In order to facilitate carrying out such tests, some background information about the course and the main photochemical reactions is supplied