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Eplerenone
General information
Eplerenone is a potassium-sparing diuretic. It is similar to spironolactone as an aldosterone antagonist, but has less affinity for androgen and progesterone receptors and may therefore have fewer adverse effects [ ].
Eplerenone is metabolized by CYP3A4 [ ] and should not be given with inhibitors of CYP3A4 because of the risk of hyperkalemia [ ].
Eplerenone has been compared with spironolactone in patients with heart failure (NYHA classes II–IV). In a dose-finding study, 321 patients maintained on ACE inhibitors and diuretics, with or without digoxin, were randomized to receive eplerenone 25–100 mg/day, spironolactone 25 mg/day, or placebo [ ]. After 12 weeks there was no improvement in heart failure in patients taking either eplerenone or spironolactone. Increases in plasma testosterone were significantly greater in men taking spironolactone than in those taking eplerenone. However, hyperkalemia was more frequent in patients taking eplerenone 100 mg/day (12%) than in those taking spironolactone 25 mg/day (8.7%). The potency of eplerenone relative to spironolactone remains to be established in patients with heart failure.
Organs and systems
Electrolyte balance
Hyperkalemia is always a consideration with spironolactone and eplerenone, but the relation between a beneficial response to eplerenone and the change in serum potassium concentration has been poorly characterized. In 397 hypertensive patients (responders and non-responders) taking eplerenone 50–200 mg/day without other susceptibility factors for hyperkalemia, eplerenone caused an increase in serum potassium concentration of 0.2 mmol/l [ ]. The blood pressure lowering effect of eplerenone did not correlate with the change in serum potassium concentration. This suggests that in patients with uncomplicated hypertension, eplerenone can be used without a significant risk of hyperkalemia.
In the Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS), the addition of eplerenone 25–50 mg/day to optimal medical therapy in patients with an acute myocardial infarction complicated by left ventricular dysfunction and heart failure significantly reduced all-cause and cardiovascular mortality [ ]. Patients with a serum potassium concentration over 5.0 mmol/l at baseline were excluded. The incidence of hypokalemia was significantly lower with eplerenone. However, there was serious hyperkalemia (serum potassium 6.0 mmol/l or more) in 5.5% of those who took eplerenone compared with 3.9% of those who took placebo.
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