Pharmacokinetics, distribution, metabolism and excretion of [ 3 H]UCN-01 in rats and dogs after intravenous administration

. Purpose: To evaluate the metabolic fate of UCN-01, a signal transduction inhibitor, blood and plasma concentrations, distribution, metabolism and excretion were investigated in rats and dogs after intravenous administration of [ 3 H]UCN-01. Methods: The radioactivity in plasma, blood and tissues was measured after intravenous administration of UCN-01. In addition, the radioactivity excreted in bile, urine and feces was also determined. Results: The radioactivity in rat and dog plasma disappeared triphasically with terminal half-lives of 21.3 and 27.2 h, respectively. The ratios of the blood-to-plasma concentrations ranged from 0.82 to 1.13 in rats and 0.81 to 1.73 in dogs. From 0.5 to 4 h after giving [ 3 H]UCN-01 to rats, the radioactivity in all tissues except the brain and testes was higher than in plasma. The highest concentration was observed in the lungs followed by the liver and kidneys. The radioactivity was mainly excreted in feces, reaching 96.0% of the radioactivity dose in rats and 78.4% in dogs up to 168 h after injection. Since the biliary excreted radioactivity was 67.2% over 48 h in bile duct-cannulated rats, most of the radioactivity excreted in feces was from biliary radioactivity. There were several metabolites in bile samples, but little UCN-01. Conclusions: UCN-01 is mainly eliminated by the liver, and there are high concentrations of radioactivity derived from [ 3 H]UCN-01 in all tissues except the brain and testes.