(7α,11α,12α,17α)-11,12-Epoxy-17-hydroxy-3-oxo-pregn-4-ene-7,21-dicarboxylic Acid Lactone, Methyl Ester is an impurity of eplerenone (E588775). Eplerenone is a selective aldosterone receptor antagonist (SARA), structurally similar to Spiranolactone. Eplerenone is used alone or in combination with other medications to treat high blood pressure. Eplerenone is in a class of medications called mineralocorticoid receptor antagonists. It works by blocking the action of aldosterone, a natural substance in the body that raises blood pressure. Molecular Formula: C24H30O6 Molecular Weight: 414.49