What is the equivalent dose of Eplerenone (generic name) when converting a heart failure patient from Spironolactone (generic name) 25mg due to a drug shortage?

Equivalent Dose When Converting from Spironolactone 25mg to Eplerenone in Heart Failure

When converting a heart failure patient from spironolactone 25mg to eplerenone due to a drug shortage, the equivalent starting dose is eplerenone 25mg once daily. 1

Dosing Conversion Protocol

• Start eplerenone at 25mg once daily as the equivalent dose to spironolactone 25mg 1
• Check renal function and serum electrolytes before initiating eplerenone 1
• Re-check renal function and serum electrolytes at 1 and 4 weeks after starting treatment 1
• Target dose for both medications is 50mg once daily, but titration should be based on patient response and laboratory monitoring 1

Monitoring Requirements

• Monitor serum potassium and renal function closely during the transition 1
• Follow-up laboratory testing schedule:
  • 1 week after conversion 1
  • 4 weeks after conversion 1
  • 1,2,3, and 6 months after achieving maintenance dose 1
  • Every 6 months thereafter 1

Special Considerations

• For patients with reduced renal function (eGFR 30-49 mL/min/1.73m²), consider starting with eplerenone 25mg every other day 1
• If potassium rises to >5.5 mmol/L, reduce dose to 25mg on alternate days 1
• If potassium rises to >6.0 mmol/L, stop eplerenone immediately 1
• If creatinine rises to >220 μmol/L (2.5 mg/dL), reduce dose to 25mg on alternate days 1
• If creatinine rises to >310 μmol/L (3.5 mg/dL), stop eplerenone immediately 1

Clinical Efficacy Comparison

• Both medications have demonstrated mortality benefits in heart failure patients 1
• Eplerenone led to a 15% relative risk reduction in death in post-MI heart failure patients (EPHESUS trial) 1
• Spironolactone showed a 30% relative risk reduction in death in severe heart failure (RALES trial) 1
• There is no evidence suggesting superior efficacy of one agent over the other in heart failure management 2

Advantages of Eplerenone vs. Spironolactone

• Eplerenone is more selective for the mineralocorticoid receptor 3
• Lower incidence of endocrine side effects compared to spironolactone 1, 3
• Particularly beneficial for male patients who experienced breast discomfort or enlargement with spironolactone 1
• Similar risk of hyperkalemia as spironolactone, requiring the same vigilant monitoring 3, 4

Common Pitfalls to Avoid

• Failure to check baseline electrolytes and renal function before conversion 1
• Inadequate monitoring of potassium and renal function after conversion 1
• Using higher starting doses in patients with reduced renal function 1
• Continuing potassium supplements without dose adjustment when switching to eplerenone 1
• Not counseling patients to avoid high-potassium foods and NSAIDs 1

Remember that both medications require careful monitoring of serum potassium and renal function, as hyperkalemia is the most serious potential adverse effect of both agents 1, 3.