Serum levels of 8-methoxypsoralen: difference between two oral methods of administration*

Abstract

Oral administration of 8-methoxypsoralen (8-MOP) followed by UV-A irradiation, about 2 h after ingestion of the drug, has been used for the past few years in the treatment of psoriasis. Serum 8-MOP levels were determined in 6 human volunteers after 2 different methods of oral administration. 8-MOP was given as an aqueous solution and as powder in gelatin capsules. The area under the curve values were higher (P < 0.05) for the solution than for the capsules, indicating a higher bioavailability. The peak serum levels were higher and were reached earlier when given as a solution. Considerable individual variation of the maximum serum levels and the area under the curve values was observed for both methods of administration, but the time required to reach the maximum serum level was more predictable after administration of the solution.