Which class of drugs is commonly used as first-line therapy to lower IOP in open-angle glaucoma?

• A. Beta-blockers
• B. Alpha2-adrenergic agonists
• C. Prostaglandin analogs
• D. Carbonic anhydrase inhibitors

Answer: (C)

In open-angle glaucoma, the aim is to lower intraocular pressure enough to protect the optic nerve. Prostaglandin analogs are commonly used as first-line therapy because they produce a strong and consistent drop in IOP with once-daily dosing and minimal systemic side effects. They work by increasing the outflow of aqueous humor through the uveoscleral pathway. The effect is typically substantial, often around a 25–35% reduction in IOP, which makes them highly effective as initial therapy.

While all drug classes lower IOP through different mechanisms, prostaglandin analogs stand out for their combination of potent effect, convenient dosing, and favorable safety profile. Other classes, like beta-blockers, reduce production of aqueous humor and can cause systemic effects (such as bradycardia or hypotension). Alpha2-adrenergic agonists can cause fatigue, allergies, and systemic effects, and carbonic anhydrase inhibitors can have systemic or local tolerability issues. These factors make prostaglandin analogs the preferred starting option in many patients.