Acetazolamide: Indications, Dosages, and Side Effects
Acetazolamide is FDA-approved for glaucoma, epilepsy, drug-induced edema, congestive heart failure, and altitude sickness, with specific dosing regimens for each indication and common side effects including paraesthesias, dysgeusia, and electrolyte imbalances. 1
Approved Indications and Dosages
Glaucoma
- For chronic simple (open-angle) glaucoma: 250 mg to 1 g daily, usually in divided doses for amounts over 250 mg 1
- For secondary glaucoma and preoperative treatment of acute congestive (closed-angle) glaucoma: 250 mg every four hours, or 250 mg twice daily for short-term therapy 1
- In acute cases, an initial dose of 500 mg followed by 125 or 250 mg every four hours may be more effective 1
Epilepsy
- Recommended daily dose: 8 to 30 mg/kg in divided doses 1
- Optimum range appears to be 375 to 1000 mg daily 1
- When used in combination with other anticonvulsants, start with 250 mg once daily 1
- Particularly effective for petit mal epilepsy in children, but also useful for other seizure types 1, 2
Congestive Heart Failure
- For diuresis: 250 to 375 mg (5 mg/kg) once daily in the morning 1
- Best results when given on alternate days or for two days alternating with a day of rest 1
- Does not eliminate the need for other therapy such as digitalis, bed rest, and salt restriction 1
Drug-Induced Edema
- 250 to 375 mg once a day for one or two days, alternating with a day of rest 1
Off-Label Indications and Dosages
Idiopathic Intracranial Hypertension (IIH)
- Used as an adjunct therapy for headache management in IIH 3
- Common starting dose is 250-500 mg twice daily, with majority of clinicians titrating the daily dose up 3
- Maximum dose of 4 g daily used in clinical trials, though many patients tolerate 1 g/day 3
Obstructive Sleep Apnea (OSA)
- European Respiratory Society conditionally recommends use only in research settings 3
- Dose range in trials: 36-1000 mg daily, with treatment periods up to 3 months 3
- Can reduce sleep apnea intensity by up to 45% in unselected groups 3
- Improves oxygen saturation and reduces oxygen desaturation index 3
Altitude Sickness
- Effective for prevention of acute mountain sickness with 48% relative risk reduction compared to placebo 4
- 250 mg/day has similar efficacy to higher doses with potentially fewer side effects 4
- Improves nocturnal oxygen saturation and reduces blood pressure increases at high altitude 3
Side Effects and Adverse Reactions
Common Side Effects
- Paraesthesias (number needed to harm: 2.3) 5
- Taste disturbances/dysgeusia (number needed to harm: 18) 5
- Polyuria (number needed to harm: 17) 5
- Fatigue (number needed to harm: 11) 5
- Vertigo and unpleasant taste 3
Serious Adverse Effects
- Electrolyte imbalances, particularly hypokalemia 1
- Metabolic acidosis 2
- Kidney stones 2
- Blood dyscrasias (rare) 2
Dose-Dependent Effects
- Risk of paraesthesias and dysgeusia increases significantly with higher doses 5
- Fatigue also shows a trend toward dose dependence 5
Important Considerations
Monitoring
- Serum electrolyte levels (particularly potassium) and blood pH should be monitored 1
- In glaucoma, careful individual attention to symptomatology and ocular tension is necessary 1
Contraindications
- Use with caution in patients with renal impairment; administration should not be more frequent than every 12 hours if creatinine clearance is less than 50 mL/min 6
- Sulfonamide allergy 3
- Kidney stones 3
- Sickle cell disease 3
Drug Interactions
- Complementary effect when used with miotics or mydriatics in glaucoma 1
- May prevent high-dose methotrexate toxicity 6
Special Populations
Pregnancy
- FDA Pregnancy Category C: Animal reproduction studies have shown adverse effects on the fetus, and there are no adequate well-controlled studies in humans 3