Furosemide vs Bumetanide
Clinical Comparison
Clinical Context
Furosemide is the default loop diuretic. However, in patients with right heart failure and gut wall oedema, oral furosemide absorption becomes unreliable. Bumetanide has 80-95% oral bioavailability regardless of gut oedema, making it the preferred switch when patients are not responding to oral furosemide.
Drug Profiles
Furosemide
Loop diuretic
Mechanism
Inhibits the Na+/K+/2Cl- co-transporter (NKCC2) in the thick ascending limb of the loop of Henle, blocking sodium and water reabsorption
Indications
- Acute and chronic heart failure (fluid overload)
- Pulmonary oedema
- Peripheral oedema
- Resistant hypertension
- Nephrotic syndrome oedema
- Acute kidney injury (to maintain urine output)
Common Doses
Oral: 20-80 mg OD/BD; IV: 20-120 mg bolus; Infusion: 5-40 mg/hour in resistant oedema
Route
Oral, IV, IM
Onset & Duration
Oral onset: 30-60 min (duration 4-6 hours); IV onset: 5 min (duration 2 hours)
Bumetanide
Loop diuretic
Mechanism
Same mechanism — inhibits NKCC2 in the thick ascending limb of the loop of Henle. 40x more potent than furosemide
Indications
- Heart failure (fluid overload)
- Resistant oedema (when furosemide oral absorption is unreliable)
- Pulmonary oedema
Common Doses
Oral: 1-2 mg OD/BD (max 5 mg/day); IV: 1-2 mg bolus
Route
Oral, IV, IM
Onset & Duration
Oral onset: 30-60 min (duration 4-6 hours); IV onset: 2-5 min (duration 2 hours)
Key Differences
| Category | Furosemide | Bumetanide |
|---|---|---|
| Oral bioavailability | 40-60% (variable, worse with gut oedema) | 80-95% (consistent, even with gut oedema) |
| Potency equivalence | 40 mg furosemide | 1 mg bumetanide (40x more potent) |
| Gut oedema | Unreliable oral absorption — may need IV | Reliable oral absorption — avoids need for IV switch |
| Clinical familiarity | Universal — standard of care | Less commonly prescribed but well-established |
| Cost | Very inexpensive | Slightly more expensive |
Oral bioavailability
40-60% (variable, worse with gut oedema)
80-95% (consistent, even with gut oedema)
Potency equivalence
40 mg furosemide
1 mg bumetanide (40x more potent)
Gut oedema
Unreliable oral absorption — may need IV
Reliable oral absorption — avoids need for IV switch
Clinical familiarity
Universal — standard of care
Less commonly prescribed but well-established
Cost
Very inexpensive
Slightly more expensive
Key Advantages
Furosemide
- Most widely used loop diuretic worldwide
- IV formulation for acute pulmonary oedema
- Flexible dosing (oral and IV)
- Very well-established — decades of experience
- Cheap and universally available
Bumetanide
- Much more predictable oral bioavailability (80-95% vs 40-60% for furosemide)
- Preferred in right heart failure with gut oedema (reliable absorption)
- 40x potency — 1 mg bumetanide = 40 mg furosemide
- Better absorption consistency means more reliable diuresis
Key Cautions
Furosemide
- Oral bioavailability only 40-60% (variable, especially in oedematous gut)
- Ototoxicity at high IV doses (especially rapid infusion)
- Hypokalaemia — monitor potassium, often co-prescribe K+ or spironolactone
- Hyponatraemia and dehydration
- Hyperuricaemia and gout exacerbation
- Renal function monitoring essential
Bumetanide
- Same electrolyte risks as furosemide (hypokalaemia, hyponatraemia)
- Ototoxicity (same class risk)
- Less prescriber familiarity (furosemide dominates practice)
- Same monitoring requirements
- Slightly more expensive than furosemide
Clinical Verdict
Start with furosemide as the default loop diuretic. Switch to bumetanide when oral furosemide is not working in a patient with gut oedema (right heart failure, fluid overload) — the more reliable oral bioavailability often avoids the need for IV diuretics.
Medical Disclaimer: This comparison is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare professional before making prescribing decisions. Verify all drug information with current clinical guidelines (BNF, NICE, SmPCs).
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