Evaluation of drug phototoxicity by photosensitization of Trichophyton mentagrophytes.

Long wave ultraviolet radiation to suspensions of T. mentagrophytes, in the presence of photosensitizing chemicals, resulted in death of the fungus as measured by loss in colony-forming ability. Photosensitization could be demonstrated, with appropriate exposures and concentrations, with chlorpromazine, promethazine, perphenazine, anthracene, sulphanilamide, trimethylpsoralen, tolbutamide, tetrachlorosalicylanilide, and tribromosalicylanilide. No phototoxicity was detected with demethylchlortetracycline and thiazides. The present system seems to be simple, reproducible, and sensitive as an in vitro screening test for the photosensitizing potential of chemicals.