Contribution of the lung to total body clearance of meperidine in the dog.

The potential role of the lung in the disposition of meperidine was examined in six conscious dogs instrumented for measurement of appropriate hemodynamic parameters. Following an intravenous bolus injection of 5 mg/kg, blood samples were collected simultaneously from cannulas placed in the left ventricle and the pulmonary artery, concurrent with the hemodynamic measurements. Pulmonary clearance, calculated from concentration differences between pulmonary arterial and left ventricular blood and pulmonary blood flow, averaged 12.1 +/- 3.70 mL/min/kg, accounting for 58 +/- 13% of the total clearance of the drug. These results help resolve differences between previously reported meperidine clearance in the dog and physiological blood flows and imply that the dog may be a poor model for this drug in humans where clearance is primarily hepatic.