The relationship between 8-methoxypsoralen skin and blood levels.

A method is described to determine the 8-methoxypsoralen (8-MOP) concentration in vivo in the skin by means of high-performance liquid chromatography (HPLC). Skin and blood samples were taken from 80 rats at specific intervals after oral administration of [3H]8-MOP. The pharmacokinetic results obtained for the skin levels were compared to the blood levels. In addition, liquid scintillation counting (LSC) was done on all the samples to compare the concentrations of 8-MOP plus metabolites to the concentrations of 8-MOP alone. There was a good correlation between the 8-MOP skin and blood levels. The values obtained with LSC were higher in function of time than the corresponding values obtained by HPLC, which indicates the presence of metabolites in both the skin and the blood. No statistically significant difference in the time of peaking was noted for the skin and blood levels. The blood levels seem to be a good parameter for the 8-MOP skin concentration.