Carbonic anhydrase inhibitors
Carbonic anhydrase inhibitors are diuretics that block the action of carbonic anhydrase. They include acetazolamide and methazo-lamide.
Carbonic anhydrase inhibitors are absorbed through the GI tract. Some systemic absorption also occurs after oph-thalmic administration. They’re distributed in tissues with high carbonic anhydrase content, such as erythrocytes, plas-ma, kidneys, eyes, liver, and muscle. Carbonic anhydrase in-hibitors are excreted by the kidneys in urine.
In the kidneys, carbonic anhydrase inhibitors decrease the availability of hydrogen ions, which blocks the sodium-hydrogen exchange mechanisms. As a result, urinary excre-tion of sodium, potassium, bicarbonate, and water increases.
In the eyes, carbonic anhydrase inhibition reduces aqueous humor production, which reduces intraocular pressure.
Carbonic anhydrase inhibitors are used for diuresis and to treat glaucoma. Acetazolamide may also be used to treat epilepsy and acute mountain sickness.
Carbonic anhydrase inhibitors produce a variety of drug interac-tions:
§ Salicylates may cause carbonic anhydrase inhibitor toxicity, in-cluding central nervous system depression and metabolic acido-sis.
§ Diflunisal may increase intraocular pressure when given with a carbonic anhydrase inhibitor.
§ Acetazolamide used concurrently with cyclosporine may in-crease cyclosporine levels and the risk of neurotoxicity.
§ Acetazolamide used concurrently with primidone may decrease serum and urine levels of primidone. (See Adverse reactions tocarbonic anhydrase inhibitors.)