Carbonic anhydrase inhibitor (systemic IOP and ICP reduction) Pregnancy: Should not be used in pregnancy, especially the first trimester; teratogenic/embryotoxic in animals.

Acetazolamide

Brand names: Diamox

Acetazolamide is a systemic carbonic anhydrase inhibitor used in ophthalmology to lower intraocular pressure in glaucoma, particularly acute angle-closure and as a short-term adjunct in raised pressure.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 250-1000 mg

Route: Oral

Frequency: Per 24 hours, in divided doses for amounts over 250 mg daily

Glaucoma (simple, acute congestive and secondary): 250-1000 mg (1-4 tablets) per 24 hours to lower raised intraocular pressure. Long-term use is contraindicated in chronic non-congestive angle-closure glaucoma. Use with particular caution in the elderly.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to acetazolamide or any excipient
Depressed sodium and/or potassium blood levels
Marked kidney and liver disease or dysfunction
Suprarenal gland failure
Hyperchloraemic acidosis
Hepatic cirrhosis (risk of hepatic encephalopathy)
Long-term use in chronic non-congestive angle-closure glaucoma
Hypersensitivity to sulphonamides

Side effects

Transient myopia, choroidal effusion, choroidal detachment
Paraesthesia (tingling in extremities), dizziness, headache, drowsiness
Metabolic acidosis, electrolyte imbalance, thirst
Nausea, vomiting, diarrhoea, taste disturbance
Blood dyscrasias (thrombocytopenia, leukopenia, aplastic anaemia, agranulocytosis); skin reactions (urticaria, Stevens-Johnson syndrome, toxic epidermal necrolysis, AGEP)

Interactions

May potentiate effects of folic acid antagonists
May potentiate hypoglycaemics and oral anticoagulants
Concurrent aspirin may cause severe acidosis and increased CNS toxicity

Clinical monograph

How it works

By inhibiting carbonic anhydrase in the ciliary body it reduces aqueous humour production, lowering intraocular pressure.

Prescribing in practice

It can cause electrolyte disturbance and metabolic acidosis and is contraindicated in marked renal or hepatic impairment and in hypokalaemia or hyponatraemia.
It is a sulfonamide derivative, so it should be avoided in patients with sulfonamide hypersensitivity, and rare but serious blood dyscrasias and severe skin reactions can occur.
Common effects include paraesthesia, taste disturbance and diuresis, and it may precipitate renal stones with prolonged use.

Monitoring

Check serum electrolytes and renal function with prolonged or higher-intensity use, and remain alert for unexplained fever, rash or bruising suggesting a blood or skin reaction.

Counselling the patient

Tingling of the hands, feet or face and an altered taste are common and usually harmless.
Report any rash, sore throat, fever or easy bruising promptly.
It increases urine output, so drink adequately and tell your doctor if you have a history of kidney stones.

Evidence & guidelines

Acetazolamide is established in UK and NICE-aligned glaucoma practice for acute lowering of intraocular pressure, especially in acute angle-closure glaucoma.

Reference: NICE CG102 Glaucoma; IIH UK guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways