[Drugs and light].

The number of drugs that are found to be photochemically unstable or able to induce phototoxic side-effects is steadily increasing. It can be difficult, however, to obtain relevant information on the photoreactivity of drugs or drug products from the commonly used handbooks. This is because of lack of standard methods of evaluation or a requirement for official specifications for a given product. The author points to the main problems connected with interactions between drugs and light in vitro and in vivo. The most obvious result of exposure to light is reduced potency of the drug because of photodecomposition. Adverse effects due to the formation of photodegradation products during storage and use have also been reported. The drug substance can further cause light-induced side-effects after administration to the patient, e.g. phototoxicity and photoallergy. More data on photoreactivity are needed in order to minimize the side-effects of frequently used drugs. The article includes a list of potential photosensitizing drug substances on the Norwegian market.