EXPERIMENTAL TOXICOLOGIC STUDIES ON 8-METHOXYPSORALEN IN ANIMALS EXPOSED TO THE LONG ULTRAVIOLET

¹ Departrnents of Dermatology, Pathology and Biochemistry, Baylor University College of Medicine, Houston, Texas

Experimental studies of the toxic effects of 8-IMP in rats and mice have been described. Included are studies of acute toxicity, subacute and chronic toxicity, effects of ultraviolet exposure upon toxicity, and acute toxicity combined with ultraviolet light exposure under a variety of conditions.

The LD5O in rats was found to be 470 ± 30 mg per kg body weight and the MLD ranged from 200 to 750 mg per kg body weight. Low doses of 8-MP can be given in mice for periods up to 1 year without apparent toxic effects.

In mice the administration of 8-MP followed by exposure to the normally safe long ultraviolet wavelengths resulted in severe toxic effects including erythema, burns and liver damage. The external application of BSA to the animals prior to ultraviolet exposure provided some protection. If the animals were irradiated and then injected with 8-MP immediately following irradiation there was no effect from the drug. Also ultraviolet irradiation of the drug before injection did not alter results. Hypophysectomy, pregnancy, ovariectomy, and adrenalectomy did not modify the action of 8-MP under the conditions of this study.