A patient started on oral acetazolamide for acute pressure control returns complaining of tingling around the mouth and fingertips. Which laboratory abnormality best explains this symptom?
- A Metabolic alkalosis with hyperkalaemia
- B Respiratory acidosis with hypernatraemia
- C Metabolic acidosis with hypokalaemia ✓
- D Metabolic acidosis with hyperkalaemia
Correct answer: C. Metabolic acidosis with hypokalaemia
Explanation
Acetazolamide inhibits carbonic anhydrase, causing bicarbonate diuresis with sodium and potassium loss. The resulting hyperchloraemic metabolic acidosis with hypokalaemia produces characteristic circumoral and digital paraesthesiae, along with malaise and polyuria. Potassium supplementation may be needed during prolonged use. Alkalosis is wrong because bicarbonate is being lost, not retained, and acetazolamide is kaliuretic rather than potassium sparing.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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