Nortriptyline therapy in elderly patients: Dosage prediction after single dose pharmacokinetic study

Summary Sixteen depressed elderly patients in hospital (mean age 81 years) received a single oral dose of nortriptyline prior to commencing treatment with this drug. Plasma nortriptyline measurements after the single dose were used to calculate the plasma drug clearance and to predict the daily dose required for each patient to achieve a steady-state concentration within the suggested therapeutic range of 50–150 µg·l^–1. Using these dosage regimes, the mean observed steady-state concentration showed a significant correlation with the predicted values (r=0.71, p<0.002). All patients had steady-state concentrations within or very close to this suggested range (mean 106, range 38–157 µg·l^–1). Use of the prediction test can prevent the development of toxic plasma concentrations and enhance the possibility of therapeutic success. Our findings suggest that a safe starting dose of nortriptyline for the elderly is 30 mg per day.