A formulary substitution is planned between loop diuretics. The approximate equipotent oral doses are:

• A Furosemide 40 mg equals bumetanide 5 mg equals torsemide 100 mg
• B Furosemide 40 mg equals bumetanide 1 mg equals torsemide 20 mg ✓
• C Furosemide 80 mg equals bumetanide 0.25 mg equals torsemide 5 mg
• D Furosemide 20 mg equals bumetanide 2 mg equals torsemide 50 mg

Explanation

The standard equianalgesic style conversion taught in Indian pharmacology texts is furosemide 40 mg, bumetanide 1 mg and torsemide 20 mg orally. Torsemide has higher and more predictable oral bioavailability than furosemide, which is erratically absorbed in edematous gut, so smaller milligram doses achieve similar natriuresis. Bumetanide is roughly forty times more potent than furosemide on a weight basis. Recognizing these ratios is commonly tested in clinical pharmacology papers.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

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