Which tricyclic antidepressant possesses the least antihistaminergic activity?

The correct answer is desipramine hydrochloride.

Desipramine hydrochloride is the least potent tricyclic antidepressant at both the histamine H1 and the muscarinic acetylcholine receptors.

The TCAs or tricyclic antidepressants refers to a category of medicines, which are used mainly as antidepressants. Desipramine is sold by the brand name Pertofrane and Norpramin among the others and is a TCA that is used in the treatment of depression.

It functions as a comparatively selective norepinephrine reuptake inhibitor, however, it also does other activities, like an antihistamine and anticholinergic effects.