Can a patient with idiopathic hyperaldosteronism (IH) taking spironolactone (aldactone) be switched directly to eplerenone (inspra) without stopping spironolactone for a few days?

Direct Switch from Spironolactone to Eplerenone

You can switch directly from spironolactone to eplerenone without a washout period, using a 2:1 dose conversion ratio (50 mg eplerenone = 25 mg spironolactone), with mandatory electrolyte and renal function monitoring at 1 and 4 weeks post-switch. 1

Conversion Protocol

Dose Equivalence

• Use a 2:1 conversion ratio: 50 mg eplerenone daily equals 25 mg spironolactone daily 1
• If the patient is on spironolactone 25 mg daily, switch to eplerenone 50 mg daily 1
• If on spironolactone 50 mg daily, switch to eplerenone 100 mg daily 1
• No washout period is required between stopping spironolactone and starting eplerenone 1

Pre-Switch Assessment

Before making the switch, verify the following parameters are acceptable 2:

• Serum potassium ≤5.0 mmol/L (do not switch if >5.0 mmol/L) 1
• Serum creatinine <220 μmol/L (2.5 mg/dL) 2
• eGFR >30 mL/min/1.73 m² (avoid both agents if <30) 1

For patients with eGFR 30-49 mL/min/1.73 m², reduce the starting eplerenone dose to 25 mg daily or every other day 1

Mandatory Monitoring Schedule

The European Society of Cardiology provides explicit monitoring requirements that apply to both drugs 2:

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

Managing Hyperkalemia After Switch

Both drugs carry similar hyperkalemia risk, though clinical trials showed comparable rates between spironolactone and eplerenone 3:

• If potassium rises to >5.5 mmol/L: Halve the eplerenone dose (e.g., 50 mg to 25 mg, or 25 mg every other day) 2
• If potassium rises to >6.0 mmol/L: Stop eplerenone immediately and monitor closely; specific treatment may be needed 2

Clinical Context for Idiopathic Hyperaldosteronism

In a prospective randomized trial specifically comparing these agents in IHA patients, direct switching was performed successfully 3:

• Two patients developed gynecomastia on spironolactone 400 mg and were switched directly to eplerenone 150 mg daily at week 16 3
• The switch resulted in resolution of gynecomastia while maintaining blood pressure control 3
• Both drugs normalized serum potassium (>3.5 mmol/L) in all IHA patients within 4 weeks 3
• Mild hyperkalemia occurred in 2/17 patients on spironolactone and 3/17 on eplerenone, demonstrating similar risk profiles 3

Key Advantages of Eplerenone

The primary indication for switching from spironolactone to eplerenone is gynecomastia or breast discomfort in men, which occurs in approximately 10% of male patients on spironolactone but is infrequent with eplerenone 2:

• Eplerenone is more selective for the mineralocorticoid receptor, avoiding sex hormone receptor effects 4, 5
• In IHA specifically, eplerenone demonstrated equivalent blood pressure control to spironolactone 3
• Systolic blood pressure decreased more rapidly with eplerenone in the IHA trial 3

Critical Pitfalls to Avoid

• Do not discontinue potassium supplements abruptly without checking baseline potassium first - both drugs are potassium-sparing 1
• Do not combine with both ACE inhibitor AND ARB - this dramatically increases hyperkalemia risk 2
• Do not switch if baseline potassium is already >5.0 mmol/L - address hyperkalemia first 1
• Do not assume eplerenone eliminates hyperkalemia risk - the rates are similar between drugs 3, 6