To investigate cutaneous UV phototoxicity 1% alpha-Terthienyl in 3% Azone gel was topically applied to mature female white guinea pigs. Investigators noted enhanced cutaneous phototoxicity with multiple applications; 3 per 24 hour period vs 1 per 24 hour period. The optimal interval between single drug application and irradiation was between 1-6 h to achieve maximum photosensitization. Clinical changes included mild erythema and inhibition of hair regrowth during the first 72 h after irradiation, with increasing erythema and edema progressing to erosion and crusting at 1 week. Clinical changes remained localized to the a-T -treated sites. Histopathologic changes at 72 h after irradiation paralleled macroscopic changes with crusting, subepidermal and intraepidermal edema and vesiculation, the presence of "sunburn" cells in the epidermis, and epidermal erosion ranging to complete epidermal degeneration.

32 microM alpha-Terthienyl was added to an emulsion of 1 micro-g/mL of glucose-6-phosphate dehydrogenase, from yeast, in a buffer of 0.1 M triethanolamine buffer, pH 7.6, and 1 g liter-’ of Tween 2O. Photooxidation was induced with UV radiation. Periodically 50 micro-L was extracted and assayed for glucose-6-phosphate dehydrogenase activity. Photoactivated alpha-terthienyl reduced glucose-6-phosphatase dehydrogenase by 76 and 97% after 36 and 90 minutes respectively.