SUNSCREEN PROTECTION AGAINST DRUG-INDUCED PHOTO-TOXICITY IN ANIMAL-MODELS

Phototoxicity was induced in animal models by photoreactive drugs in order to test sunscreen efficacy. In combination with uv-A irradiation, 8-methoxypsoralen and to a lesser extent chlorpromazine and demeclocycline elicited cutaneous erythema, edema, and ulcerative lesions in mice and guinea pigs. A commercial preparation of 5% para-amino-benzoic acid (PABA) in alcohol with proven effectiveness in preventing normal sunburn failed to protect against phototoxic drug reactions. An experimental, broad-spectrum sunscreen, PL-254-containing esters of PABA and benzophenone-blocked virtually all phototoxic response to all three drugs. Absorbance spectra of the PABA product and of PL-254 in solution and on the skin of hairless mice confirmed that PABA absorbs uv energy primarily in the uv-B range while PL-254 absorbed both uv-A and uv-B radiant energy. The uv absorbance spectra of both products on skin differed significantly from their spectra in solution. © 1979.