Systemic drug photosensitivity.

Photosensitivity as a side effect in treatment with systemic drugs occurs both as a phototoxic, non-immunologic phenomenon and as a photoallergic, immune-dependent reaction. The former principle is the more common one, and is seen with a number of non-related, widely used drug groups such as the tetracyclines, the phenothiazines, nonsteroidal antiinflammatory drugs, nalidixic acid, amiodarone and griseofulvin. For some of these drugs, for quinidine/quinine, and for the sulfonamides and related drugs, the reactions are probably also photoallergic. The majority of photosensitizing drugs have an action spectrum within UVA. Experimental studies have revealed that photoproducts and metabolites in some instances make important contributions to the biological photoreaction. For several of these drug groups, progress is presently underway in elucidating their mechanisms of action, as well as the relationship between chemical structure and in vivo photoactivity.