What is the recommended dosage of eplerenone (Eplerenone) when switching from 100mg twice daily (bid) spironolactone (Spironolactone) for a patient with idiopathic hyperaldosteronism?

Eplerenone Dosing When Switching from Spironolactone 100mg BID for Idiopathic Hyperaldosteronism

When switching from spironolactone 100mg twice daily (200mg total daily dose) to eplerenone for idiopathic hyperaldosteronism, start eplerenone at 100mg twice daily (200mg total daily dose) using a 1:1 total daily dose conversion ratio, with mandatory potassium and creatinine monitoring at 1 and 4 weeks post-switch. 1

Conversion Protocol

• Use a 1:1 conversion ratio for total daily dose in idiopathic hyperaldosteronism: 200mg spironolactone daily converts directly to 200mg eplerenone daily 1
• Administer as 100mg twice daily rather than once daily, as eplerenone often requires BID dosing for adequate blood pressure control in hyperaldosteronism 1
• No washout period is required—switch directly from spironolactone to eplerenone 2

Important Context on Dosing Ratios

The 1:1 conversion ratio for idiopathic hyperaldosteronism 1 differs from the 2:1 ratio (50mg eplerenone = 25mg spironolactone) used in heart failure 2, 3. This reflects the higher doses needed for primary aldosteronism versus heart failure, where a prospective randomized trial in idiopathic hyperaldosteronism demonstrated equivalent blood pressure control with spironolactone 25mg BID versus eplerenone 25mg BID, with doses titrated up to 400mg spironolactone or 200mg eplerenone 4. Another double-blind trial comparing spironolactone 75-225mg daily versus eplerenone 100-300mg daily in primary aldosteronism showed spironolactone had greater antihypertensive effect, suggesting eplerenone may require higher doses for equivalent efficacy 5.

Pre-Switch Safety Assessment

Before switching, verify the following parameters:

• Serum potassium must be ≤5.0 mmol/L—do not switch if higher 2, 1
• Serum creatinine must be <220 μmol/L (2.5 mg/dL) 6, 2
• eGFR must be >30 mL/min/1.73 m²—avoid both agents if lower 2
• Discontinue potassium supplements immediately at the time of switch 1

Dose Adjustment for Renal Impairment

• If eGFR is 30-49 mL/min/1.73m², consider starting at 50mg BID and titrating upward based on response and potassium levels 1

Mandatory Monitoring Schedule

Intensive early monitoring is critical to detect hyperkalemia:

• Check potassium and creatinine at 1 week post-switch 2, 1
• Recheck at 4 weeks post-switch 2, 1
• Continue monitoring at 1,2,3, and 6 months after achieving stable dose 6, 2
• Then monitor every 6 months thereafter 6, 2

Managing Hyperkalemia After Switch

If potassium rises to >5.5 mmol/L:

• Reduce eplerenone dose by 50% (from 100mg BID to 50mg BID) 2, 1
• Monitor potassium closely 6, 2

If potassium rises to >6.0 mmol/L:

• Stop eplerenone immediately 2, 1
• Monitor closely and provide specific treatment for hyperkalemia as needed 6, 2

If creatinine rises to >220 μmol/L (2.5 mg/dL):

• Halve the eplerenone dose 6

If creatinine rises to >310 μmol/L (3.5 mg/dL):

• Stop eplerenone immediately 6

Critical Pitfalls to Avoid

• Never combine eplerenone with both an ACE inhibitor AND an ARB together—this dramatically increases hyperkalemia risk 6, 1
• Avoid NSAIDs and COX-2 inhibitors—these worsen renal function and increase hyperkalemia risk 6, 1
• Do not use higher doses of ACE inhibitors (captopril ≥75mg daily, enalapril or lisinopril ≥10mg daily) as this increases hyperkalemia risk 6
• Address dehydration or diarrhea emergently—these can precipitate hyperkalemia 6

Rationale for Switching

The primary indication for switching from spironolactone to eplerenone in idiopathic hyperaldosteronism is to eliminate anti-androgenic side effects 6, 1:

• Gynecomastia occurs in 10% of men on spironolactone versus minimal occurrence with eplerenone 6, 3
• Eplerenone eliminates erectile dysfunction and menstrual irregularities associated with spironolactone 1
• In the prospective trial, 2 patients developed bilateral painful gynecomastia on spironolactone 400mg, which resolved after switching to eplerenone 150mg daily while maintaining blood pressure control 4

The risk of hyperkalemia is similar between the two agents at equivalent doses 7, 4, so the switch does not reduce this risk but improves tolerability regarding sexual side effects.