Cosopt is a combination ophthalmic drop containing dorzolamide and which other agent?

• A. Timolol
• B. Brimonidine
• C. Latanoprost
• D. Pilocarpine

Answer: (A)

The main idea here is recognizing a fixed-combination eye drop that pairs two drugs with complementary ways of lowering intraocular pressure. Cosopt combines dorzolamide with timolol. Dorzolamide is a carbonic anhydrase inhibitor that lowers the production of aqueous humor by the ciliary body. Timolol is a nonselective beta-blocker that also reduces aqueous humor formation by blocking beta receptors in the ciliary processes. Using both together gives a greater reduction in intraocular pressure than either one alone because they work by two related but distinct mechanisms.

Other agents listed act through different pathways: brimonidine is an alpha-2 adrenergic agonist, latanoprost is a prostaglandin analog that increases outflow, and pilocarpine is a miotic that also increases outflow but through a different mechanism. Cosopt’s fixed combination specifically uses dorzolamide with timolol to combine carbonic anhydrase inhibition and beta-blockade.