PLASMA-LEVELS OF 8-METHOXYPSORALEN FOLLOWING PUVA-BATH PHOTOCHEMOTHERAPY

Administration of 8-methoxypsoralen (8-MOP) in a dilute bath water sol ution is an effective therapeutic alternative to oral PUVA therapy, av oiding systemic side effects, offering better bioavailability of the p soralen and requiring much smaller amounts of UVA for induction of the rapeutic effects. To obtain exact data about the percutaneous absorpti on of 8-MOP during a psoralen bath, the plasma levels of the drug were determined in 26 patients with different skin diseases by a reverse h igh-performance liquid chromatographic method. Fifteen patients receiv ing oral PUVA therapy (0.8 mg 8-MOP/kg body weight) served as a positi ve control group. Bath solutions were prepared by diluting 15 mi of 0. 5% stock solution of 8-MOP in 150 1 of bath water (0.5 mg/l, 37 degree s C). Blood samples were drawn from patients 5, 30, 60, 120 and 180 mi n after the bath. In the oral PUVA group, blood samples were obtained 1 1/2 h after administration of the drug. In 23 of 26 patients, 8-MOP levels were undetectable in every blood sample. After 30 min, two pati ents showed detectable levels of 8-MOP (5 ng/ml, 7 ng/ml), while 60 mi n after the PUVA bath 8-MOP was detectable in only one volunteer (5 ng /ml). In patients receiving oral 8-MOP therapy, serum levels varied be tween 45 and 360 ng/ml 1 1/2 h after drug administration. Our data con firm extremely low 8-MOP levels resulting from 8-MOP bath water treatm ents and provide confirmation of the absence of systemic side effects in patients who are undergoing PUVA-bath therapy.