THE EFFECT OF TOPICAL INDOMETHACIN ON ULTRAVIOLET-RADIATION-INDUCED ERYTHEMA

Indomethacin inhibits UVB erythema but is thought not to influence UVA erythema. We have examined the wavelength dependence of the effect of indomethacin on ultraviolet radiation (UVR) erythema. Duplicate sites on the back were irradiated with a series of doses at 300 and 320 nm, or single doses at 330, 340, 350 or 370 nm. Indomethacin 1% was appli ed to sites on one side of the back after irradiation, occluded for 2 h and erythema measured at 24 h with a reflectance instrument. Indomet hacin inhibited 300 and 320 nm (UVB) erythema, had no effect at 330 an d 340 nm (UVA(2)), but augmented 350 and 370 nm (UVA(1)) erythema, The re appears to be a varied response of UVR erythema to cyclo-oxygenase inhibition at different wavelengths across the UVR spectrum. This mech anism may be deranged in certain photosensitive disorders.