ANTIMICROBIAL PHOTOSENSITIVE REACTIONS

Photosensitivity reactions are recognized as unwanted adverse effects of an array of commonly administered topical or systemic medications, including nonsteroidal antiinflammatory agents, antifungals, and antim icrobials. When a drug induces photosensitivity, exogenous molecules i n the skin absorb normally harmless doses of visible and UV light, lea ding to an acute inflammatory response. In phototoxic reactions, the d amage to tissues is direct; in photoallergic reactions, it is immunolo gically mediated. In vitro and in vivo assay systems can assist in pre dicting or confirming drug photosensitivity. The incidence of photosen sitivity reactions may be too low to be detected in clinical studies a nd may become recognized only in the postmarketing stage of drug devel opment. Some drugs have been withdrawn because of photosensitivity eff ects that appeared after general release. Photosensitivity reactions h ave been studied for a number of topical antimicrobials and for the su lfonamides, griseofulvin, the tetracyclines, and the quinolones. Incid ence and intensity of drug phototoxicity can vary widely among the dif ferent compounds of a given class of antimicrobials. When phototoxic e ffects are relatively low in incidence, mild, reversible, and clinical ly manageable, the benefits of an antimicrobial drug may well outweigh the potential for adverse photosensitivity effects.