Niazi S
J Pharm Sci. 1976 Oct;65(10):1535-6. doi: 10.1002/jps.2600651031.
The extent of first-pass metabolism of nortriptyline, calculated by comparing the areas under the plasma concentration-time curves following intravenous and oral dosing in six individuals, varied from 41 to 54%. Theoretically predicted values ranged from 41 to 61% based on a plasma flow model, indicating that the clearance takes place mainly from the plasma, which does not represent the whole blood concentration.