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Carbonic Anhydrase Inhibitor (Diuretic) Pregnancy: Avoid in first trimester — teratogenic in animal studies (limb defects); limited human data; alternative diuretics preferred

Acetazolamide (Ménière's Disease)

Brand names: Diamox

Adult dose

Dose: 250 mg once or twice daily (Ménière's); 500 mg SR once daily as alternative
Route: Oral
Frequency: Once or twice daily
Max: 1 g/day
Second-line for Ménière's disease after betahistine failure — reduces endolymph production by inhibiting carbonic anhydrase in the endolymphatic sac; also used for benign intracranial hypertension

Paediatric dose

Dose: 5–10 mg/kg/day in divided doses mg/day/kg
Route: Oral
Frequency: Two to four times daily
Max: 750 mg/day
Paediatric use: mainly for BIH/altitude sickness; Ménière's is rare in children

Dose adjustments

Renal

Avoid in eGFR <10 mL/min; risk of metabolic acidosis

Hepatic

Avoid in severe hepatic impairment — risk of hepatic encephalopathy

Paediatric weight-based calculator

Paediatric use: mainly for BIH/altitude sickness; Ménière's is rare in children

Clinical pearls

  • Ménière's disease mechanism: endolymphatic hydrops (excess endolymph) causes episodic vertigo, fluctuating sensorineural hearing loss, tinnitus, and aural fullness — acetazolamide reduces endolymph production by carbonic anhydrase inhibition in the endolymphatic sac (similar to CSF production inhibition in BIH)
  • Paraesthesia is nearly universal (>50%): tingling of extremities and perioral region — warn patients before prescribing; usually tolerable and does not require discontinuation; due to carbonic anhydrase inhibition altering neuronal pH
  • Renal stones: carbonic anhydrase inhibition reduces urinary citrate and increases urinary calcium phosphate precipitation — risk with long-term use; increase fluid intake, avoid high-dose supplements; consider alternative if stone history
  • Altitude sickness prophylaxis: 125-250 mg twice daily starting 24h before ascent — reduces incidence of AMS by accelerating ventilatory acclimatisation; ENT specialists may encounter this in travel medicine context
  • Benign intracranial hypertension (IIH): acetazolamide + weight loss is first-line (IIH Treatment Trial, NEJM 2014); reduces CSF production; important ENT overlap as papilloedema + pulsatile tinnitus can present to ENT

Contraindications

  • Sulfonamide hypersensitivity (cross-reactivity)
  • Severe renal impairment
  • Hyponatraemia/hypokalaemia
  • Addison's disease
  • Chronic angle-closure glaucoma (paradoxical effect)

Side effects

  • Paraesthesia (peripheral — very common; tingling of hands/feet/face)
  • Polyuria
  • Metabolic acidosis
  • Hyponatraemia/hypokalaemia
  • Nausea
  • Dysgeusia (altered taste of carbonated drinks)
  • Renal stones (long-term)

Interactions

  • Salicylates — increased toxicity (metabolic acidosis)
  • Lithium — increased renal lithium excretion; reduced lithium levels
  • Anticonvulsants (phenytoin) — may worsen osteomalacia

Monitoring

  • Electrolytes (Na+, K+) — monthly initially
  • Bicarbonate/acid-base status
  • FBC (rare aplastic anaemia)
  • Renal function
  • Urinary symptoms (renal stones)
  • Vestibular response (vertigo frequency/severity)

Reference: BNFc; BNF 90; BNFc; Coelho & Lalwani ENT J 2008 (Ménière's); IIH Treatment Trial (Wall et al. NEJM 2014); NICE CKS Ménière's Disease; SPC Diamox. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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