A 58-year-old man started on oral acetazolamide 250 mg six hourly for acutely elevated intraocular pressure returns after two days complaining of tingling around the mouth and fingertips, malaise, and a metallic taste. The laboratory finding most consistent with these symptoms is:
- A Metabolic alkalosis with hypochloremia
- B Respiratory alkalosis with hypocalcemia
- C Hyperchloremic metabolic acidosis with hypokalemia ✓
- D Normal anion gap acidosis with hyperkalemia
Correct answer: C. Hyperchloremic metabolic acidosis with hypokalemia
Explanation
Acetazolamide inhibits carbonic anhydrase in the proximal renal tubule, causing bicarbonate diuresis with loss of sodium, potassium, and water. The result is a hyperchloremic, normal anion gap metabolic acidosis with hypokalemia, which explains paresthesias, malaise, and altered taste. Respiratory alkalosis would be seen with hyperventilation, and acetazolamide actually causes acidosis rather than alkalosis because bicarbonate, not chloride, is lost in urine.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
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