The peripheral anticholinergic activity of tricyclic antidepressants: comparison of amitriptyline and desipramine in human volunteers.

The effects of three single oral doses (25 mg, 50 mg and 100 mg) of amitriptyline and desipramine, and of placebo, were compared on a range of cholinergic functions (resting pupil diameter, pilocarpine-evoked miosis, baseline-sweating, carbachol-evoked sweating, salivation, heart rate) in eight healthy volunteers. Three measures (pilocarpine-evoked miosis, carbachol-evoked sweating and salivation) reflected the antimuscarinic property of the antidepressants; in two tests (pilocarpine-evoked miosis and salivation) amitriptyline appeared to be more potent than desipramine. Resting pupil diameter was not affected by amitriptyline, whereas desipramine caused mydriasis, indicating that pupil size is not a reliable measure of anticholinergic activity in the case of drugs which also affect adrenergic mechanisms. Baseline-sweating and heart rate were not affected by the antidepressants.