TOPICAL CHLOROQUINE APPLIED BEFORE IRRADIATION PROTECTS AGAINST ULTRAVIOLET-B (UVB)-INDUCED AND UVA-INDUCED ERYTHEMA BUT NOT AGAINST IMMEDIATE PIGMENT DARKENING

Seventeen healthy volunteers were phototested with ultraviolet B (UVB) and UVA before and after topical treatment with chloroquine phosphate . The skin areas treated before but not after irradiation showed highe r minimal erythema dose values for UVB and UVA than control skin. The effect was clearly spectral with greater protection afforded against U VB than UVA. The immediate pigment darkening after irradiation with UV A, however, was not affected by pretreatment with the drug. The mechan ism of action for this protective effect did not seem to be related to merely absorption and screening, inhibition of the inflammatory react ion or a UV-induced effect on the stereo-isomerization of the drug.