Analysis of 8-methoxypsoralen plasma kinetics in 475 subjects: investigation of factors that could modify the bioavailability of 8-MOP

Numerous authors have described the inter-and intraindividual variations in the absorption of 8-methoxypsoralen (8-MOP). The plasma kinetics of 8-MOP were determined in 475 subjects treated or before treatment with PUVA to investigate the degree of interindividual variation in the time and the value of the maximal plasma concentration. The parameters Tmax and Cmax were evaluated after various alterations in the dose of 8-MOP to determine the effect of the alterations on these parameters. We also evaluated the importance of the intraindividual variations in Tmax and Cmax. In addition, we studied the effects of different factors on the bioavailability of 8-MOP. The study demonstrated: interindividual variations in the time and the value of the maximal plasma concentration; intraindividual variations in Cmax in subjects in whom the dose of 8-MOP was not altered; stability of Tmax in relation to the time after administration of 8-MOP and to changes in dose; and variability in the variations of Cmax following equal changes in the dose of 8-MOP. Moreover, the bioavailability of 8-MOP was not influenced by the age or sex of the subject nor by the lipid content of the diet given with the 8-MOP.