Pharmacokinetics of 8-methoxypsoralen in the dog

The pharmacokinetics of 8-MOP were studied in six dogs following intravenous administration of 2 mg kg-1. In most animals a bi-exponential decline of the plasma level profile was observed. The calculated pharmacokinetic parameters varied considerably between the different dogs. The mean half-lives of distribution and of elimination were 0.20 and 2.17 h, respectively. The average total plasma clearance was 0.51 l kg-1 h-. Following both oral and intravenous administration of doses of 1, 3, and 10 mg kg-1, non-linear kinetics were found. Non-linearity was confirmed following administration of the substance at increasing infusion rates. Finally in four dogs, extraction by the liver was calculated by measuring 8-MOP concentration in the femoral artery and in a hepatic vein after intravenous administration of 1 mg kg-1. The extraction varied from animal to animal (18 per cent to nearly 100 per cent). Administration of an additional dose of 3 mg kg-1 in two of the dogs led to a decreased extraction.