The prediction of tricyclic antidepressant plasma concentrations.

: It is possible to predict steady-state plasma nortriptyline concentrations from pharmacokinetic data obtained after giving a single oral dose. The best pharmacokinetic predictor was found to be intrinsic clearance, although simpler kinetic criteria such as the 24, 48, or 72 hour plasma concentration were almost equally valuable. Use of such a tolerance test is a simple yet powerful way of obtaining advance information on individual differences in drug disposition. From such kowledge it should be possible to individualize drug dosage regimes so as to maximize antidepressant action, while at the same time minimizing the risk of toxicity. This test could be applied routinely in the psychiatric care of both inpatients and outpatients.