Effect of Biliary Excretion on the Pharmacokinetics of Pitavastatin (NK-104) in Dogs.

Abstract

The disposition of pitavastatin and pitavastatin lactone, which are mutually converted in the circulatory system, was investigated after intravenous administration of pitavastatin in dogs equipped with chronic bile-duct catheters. The plasma concentration of pitavastatin declined three-exponentially after dosing in the dogs with both diverted and non-diverted bile-flow. The terminal elimination half-life (T1/2) of pitavastatin in the diverted and non-diverted conditions was 3.12 and 5.01 hr, and that of pitavastatin lactone 4.50 and 7.23 hr, respectively. The diverted bile-flow decreased the AUC0-24 hr for pitavastatin and its lactone to 66 and 64%, respectively. In the dogs with the diverted bile-flow, 56.1% and 4.2% of the dose was recovered in the bile as pitavastatin and its lactone, respectively. The biliary clearance (CLb) of pitavastatin and its lactone was 32.5 and 6.8 mL/min, respectively, and the CLb of pitavastatin was about 4.8-fold that of its lactone. In the dogs whose bile-flow was not diverted, the cumulative biliary excretion of pitavastatin and its lactone was estimated from the AUC0-24 hr and CLb of both forms of pitavastatin. The estimated amount was increased by 46% compared with that in the dogs with the diverted bile-flow. This indicates that the increase reflects the actual contribution of the enterohepatic circulation.