Comparison of single-dose pharmacokinetics of imipramine and maprotiline in the elderly

Pharmacokinetic profiles of imipramine and a newer tetracyclic antidepressant, maprotiline, were studied in elderly (75-83 years of age) subjects who were given a single oral dose of 125 and 175 mg, respectively, of these drugs. The apparent elimination half-life of imipramine was 20.8-34.9h (means 26.4h), its biovailability (F) was 40-64% (means 57%), and the apparent plasma clearance was from 0.27-0.57h/kg (mean 0.41h/kg). Maprotiline had a longer half-life (mean 31.5h range 20.6-51.8h, but its bioavailability (mean 50%) and plasma clearance (mean 0.49h/kg) values were in the range similar to those seen after imipramine. It appears that the elimination half-life of imipramine is longer and its plasma clearance is markedly reduced in elderly subjects when compared to values reported in young adults. Subjective clinical side effects were minimal with the two drugs. However, alterations in heart rate, blood pressure, or electrocardiogram occurred in all subjects. This suggests that caution should be exercised before initiating and during the treatment of elderly patients with these antidepressant drugs.