A study of cutaneous photosensitivity induced by amiodarone.
Amiodarone-induced cutaneous photosensitivity was studied in 12 subjects treated with the drug. The action spectrum for the abnormal response to sunlight was shown to be within the range of 335-460 (+/- 30) nm. The clinical features of the photosensitivity response suggested that it was most probably a phototoxic reaction, a conclusion supported by the results of in vitro studies which indicated activity mainly against cell membranes. Of the five in vitro models used, three--namely photohaemolysis, the inhibition of DNA synthesis in PHA stimulated lymphocytes and the killing of mouse peritoneal macrophages--provided unequivocal evidence of the phototoxic potential of both amiodarone and its major metabolite, desethylamiodarone. In each model desethylamiodarone produced a greater effect by a factor of between 2 and 10. In vitro, UV-B wavelengths produced a greater effect than UVA but the difference between the effective wavelengths in vivo and in vitro might be explained by the greater absorption of the shorter wavelength UV-B in the epidermis. Zinc oxide-containing preparations appeared to be the most effective in reducing the cutaneous photosensitivity. It is suggested that the long-term cutaneous pigmentation resulting from oral amiodarone has a significant photosensitivity component.
D000328:Adult; D000368:Aged; D000638:Amiodarone / Q000009:adverse effects* / Q000494:pharmacology; D001572:Benzofurans / Q000009:adverse effects*; D002478:Cells, Cultured; D002648:Child; D004890:Erythema / Q000209:etiology; D004912:Erythrocytes / Q000187:drug effects; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D010787:Photosensitivity Disorders / Q000139:chemically induced* / Q000517:prevention & control; D011829:Radiation Dosage; D013473:Sunscreening Agents / Q000627:therapeutic use
D001572:Benzofurans; D013473:Sunscreening Agents; D000638:Amiodarone