Pupillary dilation is commonly associated with which drug class?

• A. Anticholinergics
• B. Cholinergic Agonists
• C. Beta Blockers
• D. NSAIDs

Answer: (A)

Pupil size is controlled by autonomic input to the iris, and dilation occurs when the parasympathetic system is blocked or when the sympathetic input dominates. Anticholinergic drugs block muscarinic receptors on the iris sphincter muscle, which normally constricts the pupil. With this constricting signal blocked, the pupil cannot constrict, so it remains widened or dilates—that’s mydriasis. This is why anticholinergic agents like atropine cause noticeable pupil dilation. In contrast, cholinergic agonists stimulate the parasympathetic pathway and promote constriction, narrowing the pupil. Beta blockers and NSAIDs don’t produce dilation as a primary effect; they don’t directly override the parasympathetic constriction mechanism.