Kinetics of [ 14 C-5] 8-methoxypsoralen distribution in rabbits

Distribution, kinetics and localization of 8-methoxypsoralen (8-MOP) was determined in rabbits over 24 h following i.v. administration of [14C-5] labeled and carrier 8-MOP at respective concentration of 50 μCi and 5 mg/kg. Peak levels were reched by kidneys at 1 h (18,500 ng/g) at 2 h by liver (2,470 ng/g) and at 8 h by bile (64,000 ng/g). Muscles, lymphatic tissues and brain showed low drug uptake (800 ng/g). Endocrine organs also had low drug concentration. In gastrointestinal tract the maximum level of 8-MOP was 1,500 mg/g at 1 h in jejunum. Plasma 8-MOP concentration was 3,700 ng/ml at 5 min post injection with 100 ng/ml still detectable at 24 h. Urine label concentration peaked at 1 h (4×105 cpm/ml) and was 2×102 cpm/ml at 24 h. The intact skin concentration was at the maximum during the first 30 min (1,958 ng/g) declining progessively thereafter to 155 ng/g at 24 h. The UVA irradiated skin (320–380 nm at the rate of 14.2 mW/cm2×s-1 for 1 h) had a higher 8-MOP concentration (2,834 ng/g at 1 h and 280 ng/g at 24 h).