Adrenergic antagonists are used to lower intraocular pressure. Which drug class is commonly associated with this effect?

• A. Prostaglandins
• B. Cholinergic agonists
• C. Carbonic anhydrase inhibitors
• D. Beta-blockers

Answer: (D)

Blocking beta-adrenergic receptors in the eye reduces aqueous humor production by the ciliary body, which lowers intraocular pressure. This mechanism is why the drug class most associated with this effect is beta-blockers, such as timolol, commonly used as a first-line therapy for open-angle glaucoma or ocular hypertension. By inhibiting beta receptors on the ciliary epithelium, these agents lower adenylate cyclase activity and cAMP formation, leading to decreased secretion of aqueous humor. Clinically, this manifests as reduced IOP when used as eye drops, either alone or in combination therapy. Be mindful that systemic absorption can cause bradycardia, hypotension, or bronchospasm in susceptible individuals, so caution is advised in patients with asthma, COPD, or certain cardiac conditions. Other classes lower IOP through different mechanisms—for example, prostaglandin analogs increase outflow via the uveoscleral pathway; cholinergic agonists enhance trabecular outflow through miosis; and carbonic anhydrase inhibitors lower production but do so by enzyme inhibition rather than adrenergic blockade.