Acetazolamide
Acetazolamide is a systemic **carbonic anhydrase inhibitor** primarily used in veterinary medicine to reduce intraocular pressure in the management of **glaucoma**. It may also be used as an adjunctive treatment for metabolic alkalosis or certain seizure disorders. **Clinical Pearl:** While effective for glaucoma, topical carbonic anhydrase inhibitors (like dorzolamide or brinzolamide) are generally preferred in modern veterinary practice due to significantly fewer systemic side effects.
Mechanism: Acetazolamide reversibly inhibits the enzyme **carbonic anhydrase**. * In the eye: Inhibits carbonic anhydrase in the ciliary processes → decreases production of bicarbonate → reduces fluid transport and aqueous humor secretion → lowers **intraocular pressure (IOP)**. * In the kidneys: Inhibits carbonic anhydrase in the proximal renal tubules → decreases reabsorption of bicarbonate, sodium, and potassium → promotes alkaline diuresis and can cause mild metabolic acidosis.
Dosing by species
- Glaucoma · 5-7 mg/kg · PO · q8-12h · Cats are highly sensitive to systemic side effects; topical alternatives are strongly preferred.
- Glaucoma · 5-10 mg/kg · PO · q8-12h · Monitor for hypokalemia and metabolic acidosis.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Hepatic failure
- Renal failure
- Severe pulmonary obstruction
- Hyponatremia
- Hypokalemia
- Hyperchloremic acidosis
Adverse effects
- Polyuria
- Polydipsia
- Metabolic acidosis
- Hypokalemia
- Vomiting
- Diarrhea
- Lethargy
- Panting (especially in dogs)
Drug interactions
- Digoxin · Hypokalemia induced by acetazolamide may increase the risk of digoxin toxicity. · major
- Corticosteroids · Concurrent use increases the risk of severe hypokalemia. · moderate
- Aspirin · Increased risk of salicylate toxicity and severe metabolic acidosis. · major
- Phenobarbital · Alkalinization of urine by acetazolamide may increase the excretion of phenobarbital, potentially lowering its efficacy. · moderate
Monitoring
- Intraocular pressure (IOP)
- Serum electrolytes (especially potassium and sodium)
- Acid-base status (blood gases)
- Hydration status
Overdose
Overdosage may result in severe **metabolic acidosis**, **hypokalemia**, hyponatremia, and dehydration. Treatment consists of supportive care, including intravenous fluids to correct dehydration and electrolyte imbalances, and monitoring of acid-base status.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.