Disposition and tissue distribution of angiopeptin in the rat

The disposition and tissue distribution of angiopeptin, a long-acting octapeptide analogue of somatostatin, were studied in rats following single iv and sc administration of the drug. Similar plasma levels and excretion values of angiopeptin were observed by using radioimmunoassay and radiolabeling techniques. Angiopeptin was absorbed fairly rapidly, with a mean peak plasma level of 25 +/- 4.1 ng/ml at 10-15 min after administration. The kinetics of angiopeptin following sc administration closely resembled those following iv administration due to rapid absorption. The pharmacokinetics of angiopeptin can be described by a two-compartment model. The plasma half-life of the drug ranged from 2.6-2.9 hr when administered sc and 1.98-2.5 hr when given iv. Distribution of angiopeptin was rapid, with the highest concentration appearing in the liver. Half-lives in the liver and bile were short. Most of the drug was excreted in the feces via the bile, while approximately 10% was excreted in the urine. Angiopeptin was also found to be secreted in the saliva. TLC and HPLC of blood, urine, feces, and bile samples did not reveal the presence of any metabolites. In conclusion, the in vivo fate of angiopeptin is characterized by little or no hepatic metabolism and rapid biliary excretion.