Comparison of observed and predicted bioavailability of nortriptyline in humans following oral administration.

The first-pass equation based on the dose, hepatic blood flow, and total area under the plasma level-time curve after oral administration was used retrospectively to predict the bioavailability of nortriptyline after oral administration of 1 mg/kg-single oral doses to monozygotic and dizygotic twin pairs. The predicted values of bioavailability ranged from 45 to 85%, consistent with experimentally derived estimates of nortriptyline availability.