Drugs used for the treatment of Glaucoma

This summary covers the major classes, mechanisms, indications, and clinical guidance for drug management of glaucoma, as established in standard pharmacology texts and clinical guidelines.Drugs used for the treatment of Glaucoma are classified based on their mechanism of reducing intraocular pressure (IOP), the only proven strategy to delay glaucoma progression. The main classes and drug examples (with textbook references) are as follows:

1. Prostaglandin analogues

• Examples: Latanoprost, Travoprost, Bimatoprost
• Mechanism: Increase uveoscleral outflow of aqueous humor
• Features: First-line due to once-daily dosing, strong efficacy, favorable side-effect profile (iris pigmentation, eyelash growth, mild redness)

2. Beta-blockers

• Examples: Timolol, Betaxolol, Levobunolol
• Mechanism: Decrease aqueous humor production from the ciliary body
• Features: Commonly used; can cause bradycardia, bronchospasm (less with betaxolol, a β1 selective agent)

3. Carbonic anhydrase inhibitors (CAIs)

• Topical: Dorzolamide, Brinzolamide
• Oral: Acetazolamide, Methazolamide
• Mechanism: Inhibit carbonic anhydrase II in the ciliary epithelium, reducing aqueous humor production
• Features: Oral forms reserved for emergencies (acute angle-closure) due to systemic toxicity; topical agents preferred for routine therapy

4. Alpha adrenergic agonists

• Examples: Brimonidine (α2-selective), Apraclonidine
• Mechanism: Reduce aqueous humor production, may increase uveoscleral outflow (brimonidine)
• Features: Used alone or as adjuncts; allergic conjunctivitis and CNS effects possible

5. Parasympathomimetics (Miotics)

• Examples: Pilocarpine, Carbachol
• Mechanism: Muscarinic activation increases trabecular meshwork outflow via ciliary muscle contraction
• Features: Now less commonly used except for acute angle closure; side effects include brow ache, blurred vision, and risk of retinal detachment

6. Osmotic agents

• Examples: Mannitol, Glycerol
• Mechanism: Create an osmotic gradient pulling fluid out of the eye—used acutely for angle-closure attacks

7. Rho kinase inhibitors

• Example: Netarsudil
• Mechanism: Increase trabecular meshwork outflow and reduce episcleral venous pressure
• Features: Newer class, add-on option

8. Combination drops

• Examples: Dorzolamide + Timolol, Brimonidine + Timolol
• Mechanism: Multiple pathways targeted; convenient
• Features: Improve adherence

Treatment Strategy

• Primary open-angle glaucoma: Start with prostaglandin analogues or beta-blockers; add CAIs or alpha-agonists if needed. Miotics are used less.
• Acute angle-closure glaucoma: Oral/IV acetazolamide + osmotic agents initially, followed by pilocarpine and laser iridotomy for definitive treatment.
• If medical therapy fails, laser trabeculoplasty or surgery may be considered.

References

1. Weinreb RN, Khaw PT. Pharmacotherapy of Glaucoma. Curr Opin Ophthalmol. 2015;26(2):119–129.
2. Katzung BG. Basic & Clinical Pharmacology. 14th Edition.
3. Goodman & Gilman’s The Pharmacological Basis of Therapeutics. 13th Edition.
4. Rang HP, Dale MM. Rang & Dale’s Pharmacology. 8th Edition.