Eplerenone binds to the mineralocorticoid receptor and thereby blocks the binding of aldosterone (component of the renin-angiotensin-aldosterone-system, or RAAS). Aldosterone synthesis, which occurs primarily in the adrenal gland, is modulated by multiple factors, including angiotensin II and non-RAAS mediators such as adrenocorticotropic hormone (ACTH) and potassium. Aldosterone binds to mineralocorticoid receptors in both epithelial (e.g., kidney) and nonepithelial (e.g., heart, blood vessels, and brain) tissues and increases blood pressure through induction of sodium reabsorption and possibly other mechanisms.
Eplerenone, an aldosterone receptor antagonist similar to spironolactone, has been shown to produce sustained increases in plasma renin and serum aldosterone, consistent with inhibition of the negative regulatory feedback of aldosterone on renin secretion. The resulting increased plasma renin activity and aldosterone circulating levels do not overcome the effects of eplerenone. Eplerenone selectively binds to recombinant human mineralocorticoid receptors relative to its binding to recombinant human glucocorticoid, progesterone and androgen receptors.
Eplerenone is metabolized primarily by CYP3A4, however, no active metabolites have been identified in human plasma.
The most likely symptoms of human overdosage would be anticipated to be hypotension or hyperkalemia. However, no cases of human overdosage with eplerenone have been reported.