What is the recommended conversion dose from eplerenone (Inspra) to spironolactone (Aldactone)?

Eplerenone to Spironolactone Conversion

When converting from eplerenone to spironolactone, use a 1:1 dose conversion ratio - 25 mg of eplerenone equals 25 mg of spironolactone, and 50 mg of eplerenone equals 50 mg of spironolactone. 1

Conversion Protocol

The conversion between these two mineralocorticoid receptor antagonists follows a straightforward approach:

• Starting dose: If patient is on eplerenone 25 mg daily, convert to spironolactone 25 mg daily
• Maintenance dose: If patient is on eplerenone 50 mg daily, convert to spironolactone 50 mg daily
• For patients on alternate-day dosing: Maintain the same alternate-day schedule with equivalent doses

Monitoring After Conversion

After converting from eplerenone to spironolactone, careful monitoring is essential:

• Check renal function and serum electrolytes within 1 week after conversion
• Re-check at 4 weeks after conversion
• Continue monitoring at 1,2,3, and 6 months after achieving maintenance dose, then every 6 months thereafter 2

Important Considerations

Potency and Side Effect Differences

• While the dosing is equivalent, spironolactone has more non-mineralocorticoid receptor effects than eplerenone 3
• Spironolactone has higher incidence of endocrine side effects:
  • Gynecomastia (occurs in approximately 10% of male patients on spironolactone) 2
  • Breast tenderness
  • Sexual dysfunction

Indications for Conversion

Common reasons for switching from eplerenone to spironolactone include:

• Cost considerations (spironolactone is typically less expensive)
• Availability issues
• Formulary restrictions

Contraindications for Spironolactone

Be cautious when converting if the patient has:

• History of gynecomastia or breast pain (spironolactone may worsen these symptoms)
• Severe renal impairment (eGFR <30 mL/min/1.73m²) - both medications should be avoided 1
• Serum potassium >5.0 mEq/L

Managing Adverse Effects

If adverse effects develop after conversion to spironolactone:

• For hyperkalemia (K+ >5.5 mmol/L): Reduce dose to 25 mg on alternate days and monitor closely
• For severe hyperkalemia (K+ >6.0 mmol/L): Stop spironolactone immediately 2
• For worsening renal function (creatinine >220 μmol/L or 2.5 mg/dL): Reduce dose
• For gynecomastia or breast tenderness: Consider switching back to eplerenone 2

Efficacy Comparison

Research shows that both medications have similar efficacy in:

• Blood pressure reduction 4
• Heart failure outcomes 5
• Reduction of hospitalizations for heart failure 2

However, treatment withdrawal rates are higher with spironolactone (53%) compared to eplerenone (34%), likely due to side effect profiles 5.

Practical Conversion Algorithm

1. Confirm current eplerenone dose (25 mg or 50 mg daily)
2. Switch to equivalent spironolactone dose (25 mg or 50 mg daily)
3. Check potassium and renal function within 1 week
4. Adjust dose if needed based on laboratory results
5. Monitor for endocrine side effects, particularly in male patients
6. If side effects develop, consider dose reduction or switching back to eplerenone

This approach ensures safe and effective conversion while minimizing risks of adverse effects and maintaining therapeutic efficacy.