Which drug directly increases aqueous humor outflow?

• A. Epinephrine
• B. Timolol
• C. Pilocarpine
• D. Acetazolamide

Answer: (C)

Pilocarpine acts directly on the drainage pathway to boost outflow. It is a direct muscarinic (parasympathomimetic) agonist, so it causes the ciliary muscle to contract. This contraction pulls on the trabecular meshwork and widens the angle, opening Schlemm’s canal and reducing resistance to conventional aqueous humor outflow. In other words, its primary effect is to increase drainage rather than to decrease production.

By contrast, timolol and acetazolamide mainly decrease aqueous production rather than enhancing drainage, and epinephrine has mixed actions that do not primarily reflect a direct increase in outflow through the trabecular pathway.