ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Carbonic anhydrase inhibitor (systemic IOP and ICP reduction) Pregnancy: Avoid in first trimester (teratogenic in animals). Use only if essential.

Acetazolamide

Brand names: Diamox

Adult dose

Dose: Acute glaucoma: 500 mg IV or 500 mg oral stat; IIH: 250–1000 mg/day in divided doses
Route: IV (acute); oral (maintenance)
Frequency: Acute: single dose; Maintenance: 2–4 times daily
Max: 1 g IV (acute angle-closure); 3 g/day (IIH specialist doses)
Acute angle-closure glaucoma: 500 mg IV (over 5 min) as emergency; then 250 mg oral QDS. Idiopathic intracranial hypertension (IIH): start 250 mg BD, increase by 250 mg/week to max 2–3 g/day. Altitude sickness prevention: 250 mg BD, start 24h before ascent.

Paediatric dose

Dose: 8 mg/kg
Route: Oral or IV
Frequency: Every 6–8 hours
Max: 750 mg/day
8 mg/kg/day in divided doses every 6–8 hours (max 750 mg/day). IIH in adolescents: 25 mg/kg/day in divided doses (specialist). Weight loss and dietary management essential in paediatric IIH.

Dose adjustments

Renal

Avoid if eGFR <30 (risk of renal stones and metabolic acidosis).

Hepatic

Avoid in severe hepatic impairment.

Paediatric weight-based calculator

8 mg/kg/day in divided doses every 6–8 hours (max 750 mg/day). IIH in adolescents: 25 mg/kg/day in divided doses (specialist). Weight loss and dietary management essential in paediatric IIH.

Clinical pearls

  • Acute angle-closure: emergency — combine with pilocarpine 2%, IV acetazolamide, and arrange urgent ophthalmology
  • Paraesthesia (tingling in extremities) is expected side effect — not allergic — counsel patient
  • Carbonated drinks unpalatable (carbonic anhydrase in taste buds) — warn patient
  • Potassium supplement often needed with prolonged use (renal K+ loss)
  • IIH: weight loss is first-line intervention; acetazolamide adjunct

Contraindications

  • Severe renal impairment
  • Severe hepatic impairment
  • Sulfonamide hypersensitivity
  • Addison's disease
  • Hypokalaemia, hyponatraemia

Side effects

  • Hypokalaemia and metabolic acidosis
  • Paraesthesia (tingling in fingers/toes — common, usually benign)
  • Renal calculi
  • GI upset and anorexia
  • Drowsiness
  • Dysgeusia (carbonated drinks taste flat)
  • Stevens-Johnson syndrome (rare)

Interactions

  • Salicylates — increased acetazolamide toxicity
  • Lithium — increased urinary excretion (reduced lithium levels)
  • Antiepileptics — increased risk of metabolic acidosis
  • Potassium-depleting diuretics — additive hypokalaemia

Monitoring

  • U&E and bicarbonate
  • Renal function
  • IOP (ophthalmology)
  • Serum potassium

Reference: BNFc; BNF; NICE CG102 Glaucoma; IIH UK guidelines; BNFc. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways