The combination dorzolamide 2%/timolol 0.5% provides what dual mechanism?

• A. Beta blocker and prostaglandin analog
• B. Carbonic anhydrase inhibition plus beta blockade
• C. Alpha agonist plus cholinergic agonist
• D. Steroid and antibiotic

Answer: (B)

This combination lowers eye pressure by two ways to cut down the production of aqueous humor. Dorzolamide is a carbonic anhydrase inhibitor, so it blocks an enzyme needed to form bicarbonate in the ciliary processes. That reduction in bicarbonate leads to less aqueous humor being produced. Timolol is a nonselective beta-blocker that also decreases aqueous humor production by blocking beta receptors in the ciliary epithelium, lowering the secretory process further. Using both together gives an additive effect because they suppress aqueous humor formation through separate, complementary mechanisms. The other options describe different drug classes or effects (prostaglandin analogs change outflow via uveoscleral pathways; alpha agonists or cholinergic agents have distinct primary actions; steroids with antibiotics are not involved in aqueous production), so they don’t fit this combination.