Can a patient take Lasix (furosemide) and spironolactone together?

Yes, Lasix (furosemide) and spironolactone can and should be taken together for most patients with cirrhotic ascites or heart failure.

The combination of furosemide and spironolactone is standard therapy and often superior to either drug alone, with the optimal ratio being 100 mg spironolactone to 40 mg furosemide given as a single morning dose. 1

Recommended Dosing Strategy

Starting Doses and Titration

• Begin with spironolactone 100 mg and furosemide 40 mg together as a single morning dose 1
• Increase both medications simultaneously every 3-5 days if weight loss remains inadequate (<0.5-1 kg/day without peripheral edema) 1
• Maximum doses are spironolactone 400 mg/day and furosemide 160 mg/day, maintaining the 100:40 ratio 1

Clinical Context Determines Approach

For Cirrhotic Ascites:

• Combination therapy from the outset is preferred for recurrent or persistent ascites and provides faster control with lower hyperkalemia risk compared to spironolactone monotherapy 1
• The combination increases natriuretic effect compared to either drug alone 2
• If treating new-onset ascites, you may start with spironolactone 100 mg alone and add furosemide only if 400 mg spironolactone proves ineffective, though combination therapy upfront is increasingly preferred 2, 1

For Heart Failure:

• Start with lower doses: spironolactone 12.5-25 mg with furosemide 20-40 mg, especially if the patient is on ACE inhibitors 1
• The optimal dose of 20 mg/day furosemide plus 40 mg/day spironolactone significantly improved clinical symptoms and long-term prognosis in elderly patients with diastolic heart failure 3

Critical Monitoring Requirements

Electrolyte and Renal Function Monitoring:

• Check potassium and creatinine at 3 days, 1 week, then monthly for the first 3 months 1
• Monitor daily weights (target 0.5 kg/day loss without peripheral edema, or up to 1 kg/day with edema) 1

Hyperkalemia Risk Factors (requiring closer monitoring):

• Baseline creatinine >1.6 mg/dL 1
• Baseline potassium >5.0 mEq/L 1
• Concomitant ACE inhibitors or ARBs 1, 4
• Diabetes mellitus 1
• Elderly patients 1
• Dehydration 1

Management of Electrolyte Abnormalities:

• If potassium >5.5 mEq/L: reduce spironolactone dose or switch to every-other-day dosing 1
• If potassium <3.5 mEq/L: temporarily withhold furosemide 1
• If sodium <120-125 mmol/L: reduce or stop both diuretics 1
• If creatinine rises to >2.5 mg/dL: halve the spironolactone dose 1
• If creatinine >3.5 mg/dL: stop spironolactone immediately 1

Absolute Contraindications to Combination Therapy

Do not give this combination when:

• Creatinine clearance <30 mL/min 1
• Baseline potassium >5.0 mEq/L 1
• Patient is taking NSAIDs or COX-2 inhibitors 1

Important Practical Considerations

Administration:

• Give as a single morning dose to maximize compliance 1
• Use oral route only 1
• Discontinue or significantly reduce potassium supplements 1

Common Pitfall:

• When initiating ACE inhibitors in patients already on spironolactone, avoid potassium-sparing diuretics during ACE inhibitor initiation; wait until the ACE inhibitor dose is stable before restarting spironolactone with close monitoring 1
• The occurrence of hyperkalemia can increase even with spironolactone doses as low as 25 mg when combined with ACE inhibitors or ARBs, necessitating vigilant potassium monitoring 4

Treatment Failure Assessment:

• If ascites persists despite maximum doses (spironolactone 400 mg + furosemide 160 mg), proceed to large volume paracentesis with albumin replacement (8g per liter removed) 1
• Before declaring treatment failure, verify dietary sodium compliance by measuring 24-hour urinary sodium excretion and review all medications for NSAIDs or sodium-containing drugs 1