Carbonic Anhydrase Inhibitors

Acetazolamide is the primary drug in this class and is used primarily in the treatment of glaucoma but is considered a diuretic.  Carbonic anhydrase inhibitors, as the name implies, inhibit the enzyme carbonic anhydrase.  Inhibition of carbonic anhydrase results in decreased HCO3- reabsorption, sodium reabsorption, and hydrogen ion secretion.  Ultimately, this results in a hyperchloremic metabolic acidosis as the urine is alkalinized.  

Adverse effects include metabolic acidosis, nephrolithiasis, and hypokalemia.  These medications should be avoided in liver failure as ammonia excretion is inhibited.

Class Drugs

• Acetazolamide

Class Mechanism of Action

Inhibits carbonic anhydrase

• Carbonic anhydrase catalyzes conversion of carbon dioxide and water to bicarbonate and hydrogen ions

Carbonic anhydrase is located in the proximal tubular epithelium

• Acetazolamide decreases the exchange of sodium for hydrogen ions (increased sodium in tubules)

• Loss of bicarbonate results in hyperchloremic metabolic acidosis

• Increased potassium excretion

• Increased sodium excretion

• Increased calcium excretion

Class Applications

Altitude sickness

• Prevents cerebral edema, nausea, dizziness, and pulmonary edema

Glaucoma

• Decreases production of aqueous humor, resulting in decreased intraocular pressure

Class Adverse Effects

• Metabolic acidosis

• Hypokalemia

• Nephrolithiasis (kidney stones)

• Avoid in hepatic cirrhosis/liver failure

Decreased excretion of ammonia

Drug Table

Drug Name	Application	Comments	Image
Acetazolamide			"A Seat" "Lamb"