Antiglaucoma Drugs

Antiglaucoma drugs aim to manage intraocular pressure, preventing optic nerve damage in glaucoma. They include beta-blockers, prostaglandin analogs, alpha agonists, carbonic anhydrase inhibitors, and miotic agents. Each class targets different mechanisms to reduce intraocular pressure and preserve vision.

• β-blockers (e.g. timolol) – inhibit rate of production of aqueous humour.
• Prostaglandin analogues (e.g. latanoprost) – reduce intraocular pressure by increasing flow via uveoscleral pathway.
• Sympathomimetics (e.g. brimonidine) – increase outflow through the trabecular meshwork and reduce aqueous humour production.
• Carbonic anhydrase inhibitors (e.g. acetozolamide, dorzolamide) – reduce production of aqueous humour.
• Miotics (e.g. pilocarpine) – cause pupillary constriction thereby opening the poorly draining trabecular meshwork.

• Primary open-angle glaucoma.
• Acute closed-angle glaucoma.

• β-blockers in patients with bradycardia, heart block or uncontrolled heart failure due to systemic absorption of the drug.
• Sympathomimetics should be used with caution in patients at risk of acute closed-angle glaucoma due to mydriasis.
• Carbonic anhydrase inhibitors should be avoided in hypokalaemia and hyponatraemia.
• Miotics should be avoided in acute iritis and anterior uveitis.

• Brown pigmentation of iris and blepharitis (prostaglandin analogues).
• Ciliary spasm with headaches, ocular burning and itching (miotics).

• t½ varies. Topically administered drugs are absorbed through the cornea and predominantly metabolised in the liver.

• If carbonic anhydrase inhibitors are used long term, FBC and U&Es should be monitored.

• β-blockers should not be used in conjunction with verapamil (due to risk of AV block).

• These agents are often used in combination with the aim of reducing intraocular pressure; β-blockers and prostaglandin analogues (alone or in combination) are typically first choice.
• Acute closed-angle glaucoma is a medical emergency, requiring urgent referral to an ophthalmologist. Treatment includes IV acetozolamide, 4% pilocarpine, analgesia and anti-emetics.
• Systemic side-effects of these drugs should be considered when prescribing.