Which item from the HARDASS mnemonic is a drug that can contribute to normal anion gap metabolic acidosis when given?

• A. Acetazolamide
• B. Saline infusion
• C. Hyperalimentation
• D. Spironolactone

Answer: (A)

Normal anion gap (hyperchloremic) metabolic acidosis occurs when bicarbonate is lost or not reabsorbed, rather than an excess of unmeasured anions. Acetazolamide, a carbonic anhydrase inhibitor, blocks bicarbonate reabsorption in the proximal tubule. This causes bicarbonate to be lost in the urine, lowering plasma bicarbonate. To maintain electroneutrality, chloride is retained, increasing serum chloride and keeping the anion gap normal. Because of this bicarbonate-wasting mechanism, acetazolamide is a classic drug that can induce normal anion gap metabolic acidosis. In the HARDASS mnemonic, it’s listed as the drug associated with this acid-base disturbance.