Eplerenone (Inspra) is an aldosterone antagonist, also known as a “potassium sparing diuretic.” It acts to block the action of aldosterone inhibiting the reuptake of sodium and water. Normally, when sodium reabsorbed it is exchanged with potassium which is then excreted. Since aldosterone inhibition decreases sodium reabsorption, it also decreases potassium excretion resulting in higher serum potassium levels. Eplerenone be used to treat hypertension and congestive heart failure after myocardial infarction in certain situations.
Eplerenone was evaluated in the EPHESUS trial leading to the recommendation for its use with an ACE inhibitor prior to hospital discharge after acute coronary syndrome if there is left ventricular systolic dysfunction (ejection fraction < 40%) and either diabetes or symptomatic heart failure present and no contraindication (serum creatinine > 2.5 and or potassium > 5.0). A class effect is likely present and thus spironolactone is frequently used instead of eplerenone due to cost concerns, although there is no direct data to support this practice.
Eplerenone does not cause significant gynecomastia that can be seen with spironolactone, the most commonly used aldosterone antagonist.
Hyperkalemia and renal failure are a concern with aldosterone antagonists.