Antidepressants function most similarly to which class of autonomic drugs?

• A. Beta-adrenergic agonists
• B. Cholinergic agonists
• C. Anticholinergics
• D. Adrenergic antagonists

Answer: (C)

Antidepressants, especially some older ones like tricyclic antidepressants, have notable anticholinergic effects because they block muscarinic receptors. Blocking these receptors reduces parasympathetic (cholinergic) activity, leading to peripheral effects such as dry mouth, constipation, blurred vision, and urinary retention. That characteristic mirrors drugs that are anticholinergic, which intentionally dampen parasympathetic signaling.

Other autonomic classes described either stimulate or block different parts of the sympathetic or parasympathetic systems in ways that don’t match the typical peripheral profile of many antidepressants. For example, beta-adrenergic agonists boost sympathetic activity, cholinergic agonists enhance parasympathetic signaling, and adrenergic antagonists block sympathetic receptors. None of these produce the anticholinergic (muscarinic blockade) effects that antidepressants are known for, making anticholinergics the best fit.