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To the Editor.—
Treatment failure of psoralens and UV-A (PUVA) therapy for psoriasis may result from an inappropriate methoxsalen plasma concentration when the UV-A irradiation is actually administered.1 Indeed, there seems to be a good correlation between the methoxsalen skin concentration and the plasma concentration.2,3 Significant interindividual and intraindividual differences occur in these plasma levels, which must be standardized and optimized as far as possible if PUVA therapy is to be adequately planned and evaluated.Because major differences occur in the maximum plasma levels as well as in the time when the maximum concentrations occur as a function of the formulation or the brand of methoxsalen, we compared the pharmacokinetics of 12 different methoxsalen brands and formulations. Seven of them were commercially available brands. The other five were self-prepared formulations: oil-in-water emulsion with 20% oil, oil-in-water emulsion with 40% oil, lipo capsules (vegetable oil plus wax), lipoleci capsules
Roelandts R, Van Boven M, De Greef H, Kinget R, Adriaens P, Daenens P. Variations in Plasma Levels With 12 Different Forms of Methoxsalen. Arch Dermatol. 1984;120(10):1281-1282. doi:10.1001/archderm.1984.01650460021011