Carbonic anhydrase inhibitors are primarily used for the treatment of glaucoma. They may also be used to treat seizure disorder and acute
mountain sickness. Because they encourage solubilization and excretion of uric acid, they can be used in the treatment of gout.
Glaucoma Inhibition of carbonic anhydrase II in the ciliary processes of the eye decreases aqueous humor secretion, presumably by slowing the formation of bicarbonate ions with subsequent reduction in sodium and fluid transport.
Diuretic Carbonic anhydrase inhibitors as weak diuretics and saluretics (promotors of sodium chloride excretion). Acting principally upon the
proximal tubule of the nephron, CAIs incompletely inhibit bicarbonate reabsorption by reducing conversion of carbonic acid to CO2 at the liminal membrane, reducing intracellular conversion of CO2 back to carbonic acid after CO2 has diffused across the membrane from the lumen, and reducing transport of Na+ and bicarbonate out of the cell across the basal membrane. Lowered bicarbonate reabsorption results in decreased activity of the apical Na+/H+ exchanger which mediates diuresis. The reduced NaCl reabsorption in the proximal tubule is however partially compensated by increased NaCl reabsorption in more distal portions of the nephron (namely the
thick ascending limb of loop of Henle). The diuretic effect of CAIs is therefore middling, and the principal effect is rather urinary loss of bicarbonate and consequent decrease of blood pH (promotion of metabolic acidosis). The sulfur-containing antiseizure and antimigraine drug
topiramate is a weak inhibitor of carbonic anhydrase, particularly subtypes II and IV. Whether carbonic anhydrase inhibition contributes to its clinical activity is not known. In rare cases, the inhibition of carbonic anhydrase may be strong enough to cause
metabolic acidosis of clinical importance.
Zonisamide is another sulfur containing antiseizure drug that weakly inhibits carbonic anhydrase.
Sultiame is also an example of an anticonvulsant drug of this class.
Altitude sickness At high altitude, the partial pressure of oxygen is lower and people have to breathe more rapidly to get adequate oxygen. When this happens, the partial pressure of in the lungs (p) decreases (is "blown off"), causing a
respiratory alkalosis. This would normally be compensated by the kidney excreting bicarbonate and causing compensatory
metabolic acidosis, but this homeostatic adaptation takes several days to develop. Carbonic anhydrase inhibitors can therefore be used to hasten (or, rather, mimic)
acclimatization as these inhibit renal bicarbonate reabsorption, thus counteracting the altitude-related respiratory alkalosis. Carbonic anhydrase inhibitors have also been shown to improve
chronic mountain sickness.{{cite journal ==Contraindications==