Acetazolamide is a carbonic anhydrase inhibitor commonly used as a diuretic and to treat glaucoma and epilepsy. It works by inhibiting the carbonic anhydrase enzyme found predominantly in erythrocytes and tubular cells in the kidney. This inhibition reduces the reabsorption of sodium and bicarbonate and promotes their excretion in urine. Let's explore in more detail how acetazolamide works and its various clinical applications.

Mechanism of Action

Carbonic anhydrase is a zinc metalloenzyme that catalyzes the reversible hydration of carbon dioxide. In the kidney tubules, it helps convert carbon dioxide and water into bicarbonate and protons. The bicarbonate is then reabsorbed, while the protons combine with sodium to form sodium ions that are also reabsorbed. However, Acetazolamide binds to and inhibits the catalytic site of carbonic anhydrase isozyme II found in the renal tubular epithelial cells and erythrocytes. This inhibition blocks the reabsorption of sodium and bicarbonate and also impairs carbon dioxide hydration. As a result, more sodium, bicarbonate, and water are excreted in the urine, exerting a diuretic effect.

Uses as a Diuretic

As a potent carbonic anhydrase inhibitor, it is an effective diuretic that promotes rapid loss of sodium, chloride, and water. It finds use as a diuretic in situations requiring accelerated diuresis such as drug-induced edema, heart failure, liver cirrhosis, and nephrotic syndrome. As it interferes with renal acidification, it also renders the urine more alkaline, and hence, it may help reduce urinary calcium excretion and risk of kidney stones in some individuals. It is also used pre-operatively to reduce body water volume and promote faster recovery. Unlike loop diuretics, acetazolamide does not cause hypokalemia and works independently of aldosterone levels.