Glaucoma Medications
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Direct answer
Medical therapy for glaucoma lowers intraocular pressure either by improving aqueous outflow or by suppressing its formation, and drops are first-line for primary open-angle glaucoma. A prostaglandin analogue — latanoprost 0.005 per cent once at night — is the usual first choice, with the greatest efficacy and once-daily dosing; beta blockers (timolol 0.5 per cent twice daily), the alpha-2 agonist brimonidine and topical carbonic anhydrase inhibitors are added stepwise, and fixed-combination drops aid adherence. Systemic rescue belongs to acetazolamide, and intravenous mannitol or oral glycerol belong to the acute angle-closure crisis. Every drug carries exam-favourite contraindications: timolol in asthma and heart block, brimonidine below two years of age, acetazolamide in sulfa allergy and hypokalaemia.
What you must remember
- Latanoprost 0.005 per cent nocte: increases uveoscleral outflow; side effects are conjunctival hyperaemia, longer and darker lashes, increased iris and periocular pigmentation, reactivation of herpes simplex and uveitis, and macular oedema in pseudophakic eyes.
- Timolol 0.5 per cent twice daily reduces aqueous formation; contraindicated in asthma and chronic obstructive pulmonary disease, bradycardia, heart block and overt cardiac failure; betaxolol is beta-1 selective and the safer choice in lung disease, at some cost in efficacy.
- Brimonidine 0.2 per cent twice daily reduces formation and increases uveoscleral outflow; absolutely avoided below two years of age because of apnoea, bradycardia and hypotension in infants; somnolence and fatigue occur in children.
- Dorzolamide 2 per cent and brinzolamide (topical carbonic anhydrase inhibitors) twice to thrice daily; sulphonamide cross-reactivity, local allergy and a bitter taste are the recognised complaints.
- Pilocarpine 2–4 per cent contracts the ciliary muscle and opens the trabecular meshwork; side effects are miosis, ciliary spasm with induced myopia and brow ache; in acute angle closure it works only once pressure falls below roughly 40 mmHg, because the ischaemic sphincter will not respond.
- Acetazolamide: 250 mg orally four times daily (or 500 mg sustained-release twice daily); paraesthesia, hypokalaemia needing supplementation, renal stones, sulfa allergy and rare aplastic anaemia limit its chronic use.
- Hyperosmotics for the acute attack: mannitol 20 per cent, 1–2 g/kg intravenously over 30–45 minutes; oral glycerol 1–1.5 g/kg (contraindicated in diabetics); monitor electrolytes and cardiovascular status.
- Practical targets: a 20–30 per cent reduction from baseline intraocular pressure initially, individualised to disease stage; prostaglandin monotherapy failing means addition of a second class, not dose escalation of the same drop.
Building a regimen, then rescuing an attack
A 58-year-old teacher with early open-angle glaucoma, pressure 28 mmHg and early field loss starts latanoprost at night — one drop, explained as a lifelong commitment, with a warning about redness and lash changes. Three months later the pressure is 23 mmHg with progressing fields: add timolol 0.5 per cent twice daily after confirming no asthma or bradycardia; the fixed combination reduces his bottle count to two. If pressure still exceeds target, brimonidine or dorzolamide joins, and failure of triple therapy with progressing field is the indication for laser trabeculoplasty or filtration surgery rather than a fourth drop. Now the other emergency: a 60-year-old woman arrives with an acute angle-closure attack at 55 mmHg, a hazy cornea and a fixed mid-dilated pupil. Intravenous acetazolamide 500 mg, mannitol 1–2 g/kg, a topical beta blocker and apraclonidine buy time; pilocarpine is instilled only after the pressure drops below about 40 mmHg, when the ischaemic sphincter can constrict and pull the peripheral iris from the angle. Once the eye quiets, Nd:YAG laser peripheral iridotomy cures the pupillary block, and the fellow eye receives a prophylactic iridotomy the same week.
Where students slip
Matching drugs to contraindications is where marks leak: timolol in the asthmatic option list, brimonidine for an infant, or acetazolamide continued despite sulfa allergy or hypokalaemia. The pilocarpine trap recurs — using it as the first drop of an acute attack, when the pressure is too high for the sphincter to respond. Examiners also ask why latanoprost is dosed at night (once-daily efficacy with nocturnal pressure effect) and which drop changes iris colour irreversibly.
Frequently asked questions
Which drug is first line in open-angle glaucoma?
A prostaglandin analogue such as latanoprost 0.005 per cent once nightly, for its efficacy, once-daily dosing and systemic safety; beta blockers are the classic alternative.
Why is timolol avoided in asthma?
Non-selective beta blockade can precipitate bronchospasm and bradyarrhythmia; betaxolol, relatively beta-1 selective, is preferred when lung disease coexists.
Which glaucoma drug is contraindicated in infants?
Brimonidine — it crosses the immature blood–brain barrier and causes apnoea, bradycardia and hypotension in children under two years.
What are the dose and key adverse effects of acetazolamide?
250 mg four times daily or 500 mg sustained-release twice daily; paraesthesia, hypokalaemia, renal stones, sulfa hypersensitivity and rarely aplastic anaemia.
Why does pilocarpine fail in the first hour of acute angle closure?
At pressures above roughly 40 mmHg the iris sphincter is ischaemic and cannot constrict; the pressure must first be lowered medically, then pilocarpine pulls the iris out of the angle.
How does latanoprost lower intraocular pressure?
By increasing uveoscleral (non-conventional) outflow of aqueous through remodelling of the ciliary muscle interstices; given once at night.