Carbonic anhydrase inhibitors

Carbonic anhydrase inhibitors

Carbonic anhydrase inhibitors are diuretics that block the action of carbonic anhydrase. They include acetazolamide and methazolamide.

Pharmacokinetics

Carbonic anhydrase inhibitors are absorbed through the GI tract. Some systemic absorption also occurs after ophthalmic administration. They’re distributed in tissues with high carbonic anhydrase content, such as erythrocytes, plasma, kidneys, eyes, liver, and muscle. Carbonic anhydrase inhibitors are excreted by the kidneys in urine.

Pharmacodynamics

In the kidneys, carbonic anhydrase inhibitors decrease the availability of hydrogen ions, which blocks the sodium-hydrogen exchange mechanisms. As a result, urinary excretion of sodium, potassium, bicarbonate, and water increases.

Don’t lose your sense of humor

In the eyes, carbonic anhydrase inhibition reduces aqueous humor production, which reduces intraocular pressure.

Pharmacotherapeutics

Carbonic anhydrase inhibitors are used for diuresis and to treat glaucoma. Acetazolamide may also be used to treat epilepsy and acute mountain sickness.

Drug interactions

Carbonic anhydrase inhibitors produce a variety of drug interactions:

• Salicylates may cause carbonic anhydrase inhibitor toxicity, including central nervous system depression and metabolic acidosis.
• Diflunisal may increase intraocular pressure when given with a carbonic anhydrase inhibitor.
• Acetazolamide used concurrently with cyclosporine may increase cyclosporine levels and the risk of neurotoxicity.
• Acetazolamide used concurrently with primidone may decrease serum and urine levels of primidone. 

Warning!

Adverse reactions to carbonic anhydrase inhibitors

Adverse reactions to carbonic anhydrase inhibitors include:

• hypokalemia
• metabolic acidosis
• electrolyte imbalances.