Effect of imipramine treatment on changes in heart rate and blood pressure during postural and isometric handgrip tests.

Postural and isometric handgrip tests were performed on nine patients with panic disorder and 13 patients with major depression before and after treatment with imipramine for a mean duration of 10 weeks. There were significant increases in resting supine heart rate (HR), systolic, diastolic and mean blood pressures (SBP, DBP, MBP) after treatment. There were significant increases in HR and DBP after standing from supine posture before treatment, and after treatment, there was a significant enhancement of this tachycardia. The decrease of heart rate during the change from standing to supine posture before treatment significantly decreased further after imipramine treatment. Decreases in SBP and DBP during the change from standing to supine posture were significantly smaller during the post treatment condition. Increases in SBP during the standing isometric exercise test were smaller after treatment. These findings suggest abnormal orthostatic reflexes secondary to an altered adrenergic function and/or cholinergic supersensitivity after treatment with imipramine.