The Peripheral Anticholinergic Activity of Tricyclic Antidepressants: Comparison of Amitriptyline and Desipramine in Human Volunteers

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Abstract
Summary: 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.