If a glaucoma medication has a green cap, which drug class is most likely indicated?

• A. Cholinergic agonist
• B. Beta-blocker
• C. Prostaglandin analog
• D. Alpha agonist

Answer: (A)

A green-cap glaucoma drop is typically pilocarpine, a cholinergic agonist. It works by stimulating muscarinic receptors in the eye, causing the ciliary muscle to contract and the iris sphincter to constrict (miosis). This contraction opens the trabecular meshwork, increasing aqueous humor outflow and thereby lowering intraocular pressure. This mechanism is distinct from other classes that mainly reduce production of aqueous humor or work by different outflow pathways, which is why a green-cap cue best points to a cholinergic agent like pilocarpine. Keep in mind pilocarpine can cause pupil constriction and vision issues in low light, and is less often first-line today due to tolerance and side effects.