A patient with a documented severe sulfonamide allergy requires a loop diuretic for acute decompensated heart failure. Which loop diuretic is the appropriate choice because it lacks a sulfonamide moiety?
- A Furosemide
- B Ethacrynic acid ✓
- C Bumetanide
- D Torsemide
Correct answer: B. Ethacrynic acid
Explanation
Ethacrynic acid is the only loop diuretic that is not a sulfonamide derivative. It inhibits the NKCC2 cotransporter in the thick ascending limb like the others but has a phenoxyacetic acid structure, making it safe in true sulfonamide hypersensitivity. Furosemide, bumetanide, and torsemide all contain a sulfonamide group and are avoided in such patients.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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