Kinetics of 8-methoxypsoralen and 5-methoxypsoralen distribution in guinea pig serum, epidermis and ocular lens.

The kinetics of 8-methoxypsoralen (8-MOP) and 5-methoxypsoralen (5-MOP) distribution in serum, epidermis and lens was studied in the guinea pig following oral administration of crystalline 8-MOP or 5-MOP. Serum and epidermal levels of both psoralens, determined by high performance liquid chromatography, showed similar uptake and elimination. Lens levels of 8-MOP significantly lagged behind serum and epidermal levels. There were measurable quantities of 8-MOP in both epidermis and lens 18 h following administration. The bioavailability of 5-MOP was significantly lower than that of 8-MOP in all tissues analyzed. Possible clinical significance of these findings is discussed.