SKIN PIGMENTATION AS A PREDICTOR OF MINIMAL PHOTOTOXIC DOSE AFTER ORAL METHOXSALEN

Background and Design: Twenty-eight subjects were phototested to deter mine their erythemal responses to oral methoxsalen with W-A and UV-B i rradiation. Skin pigmentation was measured by skin reflectance at 550 and 660 nm before irradiation. The smallest W radiation dose to produc e erythema (minimal phototoxic dose and minimal erythema dose, respect ively) was determined. The serum concentration of methoxsalen was meas ured at the time of UV-A irradiation. Results: There was a positive co rrelation between skin pigmentation and both 72-hour minimal phototoxi c dose and 24-hour minimal erythema dose. No correlation was demonstra ted between methoxsalen serum concentration and minimal phototoxic dos e. The combination of skin pigmentation and methoxsalen level did notg ive a better prediction of minimal phototoxic dose than skin pigmentat ion alone. Conclusions: Skin pigmentation measurements can be used to predict the minimal phototoxic and erythema doses. Skin pigmentation m easurements are easy to perform and should be included in both phototh erapy and photochemotherapy to improve the efficiency and reliability of the treatment.