Normal healthy adult male volunteers receiving 150 mg demethylchlortetracycline four times daily were exposed to several forms of light including the fluorescent bulb, the Kromayer unit, the carbon arc lamp, and natural sunlight. All efforts to demonstrate phototoxicity of this standard agent failed until the erythema producing rays of natural sunlight were excluded with plastic film (Mylar).
When the erythema producing rays of natural sunlight are removed with plastic and the subjects exposed for from two to four hours of natural sunlight, obvious phototoxicity occurred. DMCT treated subjects demonstrated frank erythema, whereas control subjects had either pigment darkening (Meirowsky phenomena), or no response.
Attempts to reproduce this result with artificial light sources failed.
This model is proposed as a screening method to ascertain the phototoxicity of compounds absorbing light rays longer than 3100 Angstroms (A).
MAIBACH HI, SAMS WM, EPSTEIN JH. Screening for Drug Toxicity by Wave Lengths Greater Than 3,100 A. Arch Dermatol. 1967;95(1):12-15. doi:10.1001/archderm.1967.01600310018003