Pharmacology · Class
Carbonic anhydrase inhibitors !
Weak diuretics that block carbonic anhydrase: they make the urine alkaline and lower eye pressure. Used in glaucoma and altitude sickness.
Updated 2026-11-01
What they are
Sulfonamide inhibitors of carbonic anhydrase, the zinc enzyme that interconverts CO₂ and bicarbonate. Acetazolamide is the oral and IV member; dorzolamide and brinzolamide are eye drops for glaucoma.
Mechanism of action
In the proximal tubule they stop bicarbonate reabsorption, so bicarbonate, sodium and water are lost in the urine and the blood becomes mildly acidic. In the ciliary body they reduce aqueous humour production, lowering eye pressure.
Target: Carbonic anhydrase (mainly CA II and CA IV)
Drugs in this class
Others in the class
- Dorzolamide
- Brinzolamide
- Methazolamide
Test yourself
Think of the answer, then tap the question to see it.
What acid-base disorder do carbonic anhydrase inhibitors cause?
Hyperchloraemic (normal anion gap) metabolic acidosis, from loss of bicarbonate in the urine.
Why does acetazolamide help with acute mountain sickness?
The mild metabolic acidosis it causes stimulates breathing, which offsets the respiratory alkalosis of altitude and speeds acclimatisation.
Why are carbonic anhydrase inhibitors avoided in cirrhosis?
Alkaline urine reduces ammonia excretion; the extra ammonia can trigger hepatic encephalopathy.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - ACETAZOLAMIDE tablet (DailyMed (U.S. National Library of Medicine), 2026); Acetazolamide: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2017); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.