What is the typical dosing regimen for spironolactone (Spironolactone) and Lasix (Furosemide) for managing ascites?

Dosing of Spironolactone and Furosemide for Ascites

The optimal dosing regimen for ascites management begins with spironolactone 100 mg daily, with addition of furosemide 40 mg daily if needed, gradually titrating both medications while maintaining a 100:40 mg ratio up to maximum doses of spironolactone 400 mg and furosemide 160 mg daily. 1, 2

Initial Treatment Approach

First-Line Therapy

• Start with spironolactone 100 mg once daily as monotherapy 1, 2
• Restrict sodium intake to 2 g (90 mmol) per day 1, 2
• Allow 3-5 days between dose adjustments due to spironolactone's long half-life 1
• Monitor for clinical response (weight loss, decreased abdominal girth)

Adding Furosemide

• If inadequate response to spironolactone alone after 3-5 days, add furosemide 40 mg once daily 1, 2
• Maintain the 100:40 mg ratio of spironolactone to furosemide when increasing doses 1, 2
• Single morning dosing of both medications maximizes compliance 1

Dose Titration Protocol

Stepwise Dose Increases

1. Initial: Spironolactone 100 mg daily
2. If inadequate response: Add furosemide 40 mg daily
3. Titrate upward every 3-5 days as needed:
   • Spironolactone 200 mg + Furosemide 80 mg
   • Spironolactone 300 mg + Furosemide 120 mg
   • Spironolactone 400 mg + Furosemide 160 mg (maximum doses) 1, 2

Target Weight Loss

• Without peripheral edema: 0.5 kg/day 2, 3
• With peripheral edema: No specific limit, but monitor carefully 2

Monitoring Parameters

Laboratory Monitoring

• Check serum electrolytes, BUN, and creatinine at baseline and 3-5 days after each dose adjustment
• Monitor for:
  • Hypokalemia (may require temporary withholding of furosemide)
  • Hyperkalemia (may require reduction in spironolactone dose)
  • Rising creatinine (may indicate over-diuresis)
  • Hyponatremia (especially if sodium <125 mmol/L) 1, 2

Clinical Monitoring

• Daily weight measurements
• Abdominal girth measurements
• Assessment for peripheral edema
• Evaluation for signs of hepatic encephalopathy

Special Considerations

Refractory Ascites

• For tense ascites, consider large-volume paracentesis (LVP) with albumin replacement (8 g/L of fluid removed) for volumes >5L 1, 2
• After LVP, continue diuretic therapy to prevent reaccumulation 1

Hyponatremia Management

• If serum sodium 121-125 mmol/L: Consider reducing diuretic dose
• If serum sodium <120 mmol/L: Stop diuretics and consider volume expansion 2
• Fluid restriction (1-1.5 L/day) only for severe hyponatremia (<125 mmol/L) 2

Adverse Effects

• Common side effects of spironolactone include gynecomastia, impotence, menstrual irregularities
• Tamoxifen 20 mg twice daily may help manage gynecomastia 1
• Amiloride (10-40 mg/day) can be substituted for spironolactone if side effects are intolerable 1

Evidence-Based Rationale

Research has demonstrated that spironolactone is more effective than loop diuretics as monotherapy for ascites 1, 4. A randomized study showed that spironolactone alone was as effective as combination therapy for moderate ascites, with fewer dose adjustments required 5. However, the combination of spironolactone and furosemide increases the natriuretic effect while balancing potassium levels 4.

The 2021 AASLD practice guidance and 2025 Praxis Medical Insights both support starting with spironolactone and adding furosemide if needed, while maintaining the 100:40 mg ratio during dose escalation 1, 2.