acetazolamide

Acetazolamide is a carbonic anhydrase inhibitor in the sulfonamide class. It acts mainly in the proximal tubule to inhibit carbonic anhydrase, reducing bicarbonate reabsorption and promoting bicarbonate-rich urine. The resulting mild metabolic acidosis contributes to diuresis and electrolyte changes. By decreasing aqueous humor production in the ciliary body, it also lowers intraocular pressure, providing a therapeutic effect in glaucoma.

Medical uses include open-angle glaucoma as an adjunct to other therapies; prevention and treatment of altitude sickness; and management of idiopathic intracranial hypertension by reducing cerebrospinal fluid production. It may be used off-label for urinary alkalinization in certain toxic ingestions and as an adjunct anticonvulsant in some seizure disorders.

Dosing varies by indication. For glaucoma, 250 mg every 6 hours (approximately 1 g/day). For altitude sickness prophylaxis, 125 mg twice daily starting one day before ascent and continuing for 2–3 days at altitude. If symptoms develop, 250 mg every 6 hours may be used for 24–48 hours before tapering.

Adverse effects include paresthesias, fatigue, dizziness, and nausea; metabolic acidosis with hyperchloremia; electrolyte disturbances such as hypokalemia; and urinary stone formation due to alkaline urine. Hypersensitivity reactions can occur in individuals with sulfonamide sensitivities. Caution is advised in hepatic impairment and during pregnancy or lactation.

Pharmacokinetics: orally absorbed, with peak levels in 2–4 hours; largely excreted unchanged in urine; elimination half-life about 8–12 hours. Dose adjustments are needed in renal impairment. Contraindications include hypersensitivity to acetazolamide or other sulfonamides and severe renal dysfunction. Interactions include additive diuretic effects and altered acid-base balance; monitor electrolyte status and urine pH.