Nature and Incidence of Photosensitivity Reactions to Demethylchlortetracycline

Abstract

Several recent case reports^1-3 have indicated the occurrence of photosensitivity reactions in patients taking demethylchlortetracycline.^* This study was undertaken to determine the incidence of such reactions, the relationship between their occurrence and dosage of the drug, the responsible spectral range, and the nature of these reactions, whether photoallergic or phototoxic.⁴ Method I. Determination of Incidence of Demethylchlortetracycline Photosensitivity Reactions.— (A) Using Artificial Light Sources: One hundred white men, who had not been exposed to sunlight for the preceding 6 months were included in this phase of the study. The minimal erythema dose (M.E.D.), which is defined as that amount of ultraviolet light required to produce a barely perceptable erythema on the skin 24 hours after exposure (1+) was determined for each subject. This was accomplished by giving graded exposures of ultraviolet light to skin test sites on the upper back, as emitted by a Westinghouse fluorescent