Serum Levels of 8-Methoxypsoralen in Two Different Drug Preparations: Correlation with Photosensitivity and UV-A Dose Requirements for Photochemotherapy

In a quantitative study we have compared the serum levels, the time course and the photosensitizing capacity of a conventional crystalline 8-methoxypsoralen brand and an investigational liquid formula. Evidence is presented showing that the liquid preparation is superior to the crystalline form: it peaks earlier after ingestion, it produces higher and more reproducible serum concentrations and thus a more constant degree of photosensitization, it is eliminated more rapidly from the blood, and it requires a lower UV-A dose for eliciting photosensitivity reactions aiming at a reduction of the total cumulative UV-A dose required for clearing psoriasis