Which medication class can cause normal anion gap metabolic acidosis by inhibiting carbonic anhydrase?

Which medication class can cause normal anion gap metabolic acidosis by inhibiting carbonic anhydrase?

• A. Loop diuretics
• B. ACE inhibitors
• C. Carbonic anhydrase inhibitors (e.g., acetazolamide)
• D. Angiotensin receptor blockers

Answer: (C)

Normal anion gap metabolic acidosis happens when bicarbonate is lost or not adequately reabsorbed, and chloride rises to preserve electroneutrality, so the overall anion gap remains normal. Carbonic anhydrase in the proximal tubule normally helps reclaim filtered bicarbonate. When a carbonic anhydrase inhibitor is used, bicarbonate reabsorption is impaired, bicarbonate is lost in the urine, serum bicarbonate falls, and a hyperchloremic (normal-AG) metabolic acidosis ensues. This is a classic effect of acetazolamide and other carbonic anhydrase inhibitors, often with an initial alkaline urine due to bicarbonate in the filtrate. The other medications listed do not produce this bicarbonate-wasting mechanism: loop diuretics typically cause metabolic alkalosis through volume contraction and hydrogen/potassium loss, while ACE inhibitors and ARBs do not cause this form of acidosis via carbonic anhydrase inhibition.

Normal anion gap metabolic acidosis happens when bicarbonate is lost or not adequately reabsorbed, and chloride rises to preserve electroneutrality, so the overall anion gap remains normal. Carbonic anhydrase in the proximal tubule normally helps reclaim filtered bicarbonate. When a carbonic anhydrase inhibitor is used, bicarbonate reabsorption is impaired, bicarbonate is lost in the urine, serum bicarbonate falls, and a hyperchloremic (normal-AG) metabolic acidosis ensues. This is a classic effect of acetazolamide and other carbonic anhydrase inhibitors, often with an initial alkaline urine due to bicarbonate in the filtrate. The other medications listed do not produce this bicarbonate-wasting mechanism: loop diuretics typically cause metabolic alkalosis through volume contraction and hydrogen/potassium loss, while ACE inhibitors and ARBs do not cause this form of acidosis via carbonic anhydrase inhibition.