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Part V: Clinical Applications of Psoralens, and Related Materials: Increased Erythema Threshold Six Weeks after a Single Exposure to Sunlight Plus Oral Methoxsalen11From the Division of Dermatology, University of Oregon Medical School, Portland, Oregon.

1959; Elsevier BV; Volume: 32; Issue: 2 Linguagem: Inglês

10.1038/jid.1959.54

1523-1747

John D Imbrie, Farrington Daniels, Lester Bergeron, Carl E. Hopkins, Thomas B. Fitzpatrick,

Plant chemical constituents analysis

After the introduction of 8-methoxypsoralen into the United States for the treatment of vitiligo it was observed that albino and normal patients appeared to have an increased tolerance of solar exposure following ingestion of the drug. The testimonial evidence on this point was extensive and enthusiastic. Preliminary studies indicated that 8-methoxypsoralen taken orally two or three hours before exposure increased skin tolerance to ultraviolet radiation and also promoted melanin pigmentation (1). The impression that 8-methoxypsoralen plus graded exposures to sunlight markedly promoted tolerance to ultraviolet light was reported by many patients and observed by many clinicians. While it was assumed that this protection was mediated by an increased melanin deposition in the skin, the possibility of other more complicated mechanisms has been repeatedly postulated by investigators in the field. Short term trials during 1956 at the Arizona State Prison and the Idaho State Prison did not produce striking evidence of altered responses in men receiving 10, 20 and 40 milligrams of 8-methoxypsoralen (2). In the earlier study in 1955 (1), marked potentiation of erythema was observed and it was concluded at that time that 8-methoxypsoralen does not have a specific pigment promoting effect in combination with ultraviolet light, but simply potentiates all or most of the normal skin responses to ultraviolet light. Because most of the testimonial evidence in patients had been accumulated by prolonged use it was believed possible that discrepancies between the clinical impression of benefit and the lack of evidence in short term but well controlled experiments on large numbers of men might be explained by mechanisms which were not active during the short term trials.