Evaluating off-label uses of acetazolamide

PURPOSE: Current off-label uses of acetazolamide in hospitalized patients are reviewed. SUMMARY: Acetazolamide is a carbonic anhydrase inhibitor typically used for indications including epilepsy, glaucoma, edema, and altitude sickness but it may be prescribed in hospitalized patients for off-label indications. It inhibits carbonic anhydrase, which leads to reduced hydrogen ion secretion in the proximal renal tubule, resulting in increased bicarbonate and cation excretion and causing urinary alkalization and diuresis. In addition, acetazolamide decreases the production of cerebrospinal fluid (CSF) and aqueous humor, reducing intracranial pressure (ICP) and intraocular pressure. This allows acetazolamide to be used for treatment of idiopathic intracranial hypertension and elevated ICP due to CSF leaks to avoid invasive procedures. It is a sulfonamide derivative, with dosages ranging from 250 to 4,000 mg daily divided every 6-12 hours. The plasma half-life is 4-8 hours, though the pharmacologic effects of acetazolamide last longer. Acetazolamide is highly protein bound and primarily eliminated by the kidneys, so administration should not be more frequent than every 12 hours if creatinine clearance is less than 50 mL/min. Limited literature exists describing the optimal patients to receive acetazolamide therapy. CONCLUSION: The potential benefits of acetazolamide include ventilator weaning for chronic obstructive pulmonary disease patients, avoidance of invasive procedures in patients with a CSF leak or elevated ICP, and prevention of high-dose methotrexate toxicity and contrast-induced nephropathy. Uncertainty remains regarding the selection of patients who would best benefit from acetazolamide use.