A patient on long-term furosemide therapy develops muscle weakness and ECG changes showing flattened T waves and prominent U waves. Which electrolyte disturbance is MOST responsible?
- A Hypokalaemia ✓
- B Hyponatraemia
- C Hypercalcaemia
- D Hypermagnesaemia
Correct answer: A. Hypokalaemia
Explanation
Loop diuretics inhibit the Na-K-2Cl cotransporter in the thick ascending limb of Henle, causing increased potassium loss in urine. Hypokalaemia classically produces muscle weakness, cramps, and the ECG triad of flattened T waves, U waves, and prolonged QT. Furosemide also causes hypomagnesaemia, which further worsens hypokalaemia by impairing renal potassium conservation.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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