Electrocardiographic effects of nortriptyline, phenelzine, and placebo under optimal treatment conditions.

The authors treated 44 outpatients 55 years old or older who were suffering from major depression with either nortriptyline, phenelzine, or placebo for 7 weeks. Plasma levels of nortriptyline were kept between 50 and 170 ng/ml, and platelet monoamine oxidase (MAO) inhibition in phenelzine-treated patients was kept between 70% and 80%. ECGs were compared before and after treatment. Nortriptyline produced statistically significant increases in both the heart rate and the PR interval, although none was outside the normal range. Phenelzine produced a significant decrease in the QT interval. None of the patients had pathological ECG changes under the closely monitored treatment conditions of this study.