A patient with open-angle glaucoma is prescribed a drug that reduces intraocular pressure by increasing aqueous humor outflow through the trabecular meshwork AND directly decreasing aqueous production. Which receptor mechanism accounts for BOTH these actions simultaneously?

• A Alpha-2 adrenergic agonism reducing aqueous production and increasing uveoscleral outflow ✓
• B M3 muscarinic agonism causing ciliary muscle contraction
• C Beta-1 adrenergic blockade reducing aqueous secretion from ciliary epithelium
• D Carbonic anhydrase inhibition reducing bicarbonate-dependent aqueous formation

Explanation

Alpha-2 adrenergic agonists (e.g., brimonidine, apraclonidine) reduce IOP by two mechanisms: presynaptic alpha-2 activation in the ciliary body reduces aqueous humor production, and they also increase uveoscleral outflow. Beta blockers (timolol) reduce only secretion, while pilocarpine (M3) increases trabecular outflow only through ciliary muscle contraction. Carbonic anhydrase inhibitors act solely on secretion via bicarbonate inhibition.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.