The electrocardiographic and anticholinergic effects of trazodone and imipramine in man

The electrocardiographic and anticholinergic effects of trazodone (150 mg) and imipramine (75 mg) were investigated in 8 healthy volunteers. Both agents increased the QTc interval and decreased T wave height, but the effects occurred earlier with trazodone (from 30 min onwards) than with imipramine (150 and 180 min after dosing). Both drugs decreased heart rate, imipramine at 30 and 60 min and trazodone at 90 min. After 120 min, heart rate began to increase with imipramine an effect which was not seen with trazodone. Salivary volume was significantly decreased by imipramine at 120 and 180 min whereas trazodone did not influence salivary volume. Plasma levels of trazodone and imipramine were significantly related to the decrease in T wave amplitude. The increase in QTc interval correlated significantly with the plasma level of imipramine. These results suggest that trazodone, like the tricyclic antidepressants prolongs ventricular repolarization; but, in contrast to imipramine, it does not have anticholinergic activity.