Sunscreen protection against drug-induced phototoxicity in animal models
Akin, F.J.; Rose, A.P.; Chamness, T.W.; Marlowe, E.
Toxicology and Applied Pharmacology 49(2): 219-224
1979
ISSN/ISBN: 0041-008X PMID: 115110 Document Number: 145331
Sunscreen designed for prevention of normal sunburn are often ineffective in preventing phototoxic drug reactions. PABA [p-aminobenzoic acid] in solution absorbs UV light in the UV-B region (290-320 nm) but does not UV-A (320-400 nm) radiation responsible for most drug-induced phototoxicity. Phototoxicity was induced in animal models by photoreactive drugs 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% PABA in alcohol with proven effectiveness in preventing normal sunburn failed to protect against phototoxic drug reactions. An experimental broad-spectrum sunscreen, PL-254.sbd.containing esters of PABA and benzophenone.sbd.blocked virtually all phototoxic response to all 3 drugs. Absorbance spectra of the PABA product and of PL-254 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.