Antiglaucoma Therapy: Topical And Systemic

Treatment of glaucoma is based on the assumption that lowering intraocular pressure currently is the most important thing an eye doctor can do for the patient. At the present time, benefits such as improved blood flow or direct neuroprotection of retinal ganglion cells are secondary considerations when choosing primary therapy for patients with ocular hypertension or open-angle glaucoma.

Medications for glaucoma management may be divided into six classes;

1. Beta-adrenergic antagonist (suppresses aqueous humor formation).
2. Prostaglandins (increases uveoscleral outflow).
3. Carbonic anhydrase inhibitors (inhibits aqueous humor formation).
4. Sympathomimetic agonists (increases trabecular and uveoscleral outflow).
5. Alpha-adrenergic agonists (reduces aqueous formation and increases outflow).
6. Hyperosmotic agents (reduces the water content of the vitreous).

Beta-blockers

The usual dosage of beta-blockers is one drop two times a day and examples include the following;

• Timolol; Available as 0.25% and 0.5% solutions and ophthalmic gels. It is contraindicated in patients with bronchial asthma and heart blocks.

• Betaxolol; Available as 0.25% and 0.5% ophthalmic solution.

• Carteolol; Available as 0.1% ophthalmic solution.

• Levobunolol; Available as 0.25% and 0.5% ophthalmic solution.

• Metipranol; Available as 0.1%, 0.3% and 0.6% ophthalmic solution.

Prostaglandins

The usual dosage is one drop once daily preferably at bedtime or in the evening. They are the most effective (as well as expensive). Examples include the following: 

• Latanoprost (Xalantan); Available as 0.005% ophthalmic solution.

• Xalcom (Latim); Available as 0.005% latanoprost and 0.5% timolol maleate ophthalmic solution.

• Bimatoprost (Lumigan); Available as 0.03% ophthalmic solution.

• Travoprost (Travatan); available as 0.004% ophthalmic solution.

                                                    

Carbonic Anhydrase Inhibitors

• Acetazolamide (Diamox); This is the most frequently used oral glaucoma agent and is available as 125mg, 250mg and 500mg tablets (250mg every six hour or 500mg twice daily), as 250-500mg powder in 5-10ml distilled water parenterally or as 5% ophthalmic solution (one drop 2-3 times daily).

• Dorzalamide (Dorzox); Avaliable as 2% ophthalmic solution (one drop three times daily) or as 2% dorzolamide with 0.5% timolol maleate (one drop two times daily).

• Brinzalamide: Available as 1% ophthalmic suspension (one drop three times daily).

• Methazolamide; Available as 25mg and 50mg oral tablets (50-100mg 2-3 times daily).

 

Sympathomimetics

• Epinephrine; Available as 0.5-2% hydrochloride, borate and bitartrate salts solution (one drop three times daily).

• Dipivefrine; Available as 0.1% ophthalmic solution (one drop two times daily).

Alpha-adrenergic Agonists

• Brimonidine (Alphagan); available as 0.2% topical solution (one drop twice daily). Also available in combination with 0.5% timolol maleate (one drop twice daily).

• Clonidine; Available as 0.125%, 0.25% and 0.50% ophthalmic solution (one drop three times daily).

Hyperosmotic Agents

Hyperosmotic agents are administered orally and intravenously for short-time management of acute glaucoma. Because their effect is short, there should be another means of lowering the intraocular pressure when they are being administered. Examples include the following;

• Mannitol (Osmitrol); Available as 15-20% intravenous solution (2.5-7.0ml/kg). The infusion can be terminated when intraocular pressure falls to the desired level.

• Glycerin (Glycerol, Glyrol or Osmoglyn); Should not be used in diabetic patients as it is metabolized to glucose (ismotic is preferred). It is available as 50% and 75% oral solution with lime flavored (1.5-3.0ml/kg every hour).

• Isosorbide(Ismotic); Available as 45% oral solution with mint flavored (1-2g/kg 2-4 times daily).

• Urea powder; Available as 30% intravenous solution (0.5-2g/kg IV).