A 40-year-old man with POAG is prescribed dorzolamide 2% three times daily. He reports a bitter taste and mild fatigue after starting the medication. What is the mechanism by which topical dorzolamide lowers intraocular pressure?

• A Reduces episcleral venous pressure
• B Increases trabecular outflow by relaxing the meshwork
• C Constricts the pupil improving outflow
• D Reduces aqueous production by inhibiting carbonic anhydrase in the ciliary epithelium ✓

Explanation

Topical carbonic anhydrase inhibitors like dorzolamide reduce aqueous humour production by inhibiting carbonic anhydrase isoenzyme II in the ciliary epithelium, decreasing bicarbonate ion formation and thus fluid transport. Systemic CAIs have more side effects; topical formulations cause local irritation and bitter taste. They do not alter trabecular outflow, pupil size, or episcleral venous pressure.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.