|Pharmacotherapeutic group: aldosterone antagonists, ATC code: C03DA04Eplerenone has relative selectivity in binding to recombinant human mineralocorticoid receptors compared to its binding to recombinant human glucocorticoid, progesterone and androgen receptors. Eplerenone prevents the binding of aldosterone, a key hormone in the renin-angiotensin-aldosterone-system (RAAS), which is involved in the regulation of blood pressure and the pathophysiology of cardiovascular disease.Eplerenone 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. In dose-ranging studies of chronic heart failure (NYHA classification II-IV), the addition of eplerenone to standard therapy resulted in expected dose-dependent increases in aldosterone. Similarly, in a cardiorenal substudy of EPHESUS, therapy with eplerenone led to a significant increase in aldosterone. These results confirm the blockade of the mineralocorticoid receptor in these populations.Eplerenone was studied in the Eplerenone Post-acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS). EPHESUS was a double-blind, placebo-controlled study, of 3 year duration, in 6632 patients with acute myocardial infarction (MI), left ventricular dysfunction (as measured by left ventricular ejection fraction [LVEF] ≤40%), and clinical signs of heart failure. Within 3-14 days (median 7 days) after an acute MI, patients received eplerenone or placebo in addition to standard therapies at an initial dose 25 mg once daily and titrated to the target dose of 50 mg once daily after 4 weeks if serum potassium was < 5.0 mmol/L. During the study patients received standard care including acetylsalicylic acid (92%), ACE inhibitors (90%), ß-blockers (83%), nitrates (72%), loop diuretics (66%), or HMG CoA reductase inhibitors (60%). In EPHESUS, the co-primary endpoints were all-cause mortality and the combined endpoint of CV death or CV hospitalisation; 14.4 % of patients assigned to eplerenone and 16.7 % of patients assigned to placebo died (all causes), while 26.7 % of patients assigned to eplerenone and 30.0 % assigned to placebo met the combined endpoint of CV death or hospitalisation. Thus, in EPHESUS, eplerenone reduced the risk of death from any cause by 15% (RR 0.85; 95% CI, 0.75-0.96; p= 0.008) compared to placebo, primarily by reducing cardiovascular (CV) mortality. The risk of CV death or CV hospitalisation was reduced by 13% with eplerenone (RR 0.87; 95% CI, 0.79-0.95; p=0.002). The absolute risk reductions for the endpoints all cause mortality and CV mortality/hospitalisation were 2.3 and 3.3%, respectively. Clinical efficacy was primarily demonstrated when eplerenone therapy was initiated in patients aged < 75 years old. The benefits of therapy in those patients over the age of 75 are unclear. NYHA functional classification improved or remained stable for a statistically significantly greater proportion of patients receiving eplerenone compared to placebo. The incidence of hyperkalaemia was 3.4 % in the eplerenone group vs 2.0 % in the placebo group (p < 0.001). The incidence of hypokalaemia was 0.5 % in the eplerenone group vs 1.5 % in the placebo group (p < 0.001).No consistent effects of eplerenone on heart rate, QRS duration, or PR or QT interval were observed in 147 normal subjects evaluated for electrocardiographic changes during pharmacokinetic studies.In the EMPHASIS-HF trial (Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure) the effect of eplerenone when added to standard therapy was investigated on clinical outcomes in patients with systolic heart failure and mild symptoms (NYHA functional class II). Patients were included if they were at least 55 years old, had a left ventricular ejection fraction (LVEF) ≤ 30% or LVEF ≤ 35% in addition to QRS duration of > 130 msec, and were either hospitalized for cardiovascular (CV) reasons 6 months prior to inclusion or had a plasma level of B-type natriuretic peptide (BNP) of at least 250 pg/ml or a plasma level of N-terminal pro-BNP of at least 500 pg/ml in men (750 pg/ml in women). Eplerenone was started at a dose of 25 mg once daily and was increased after 4 weeks to 50 mg once daily if the serum potassium level was < 5.0 mmol/L. Alternatively, if the estimated GFR was 30-49 ml/min/1.73 m2, eplerenone was started at 25 mg on alternate days, and increased to 25 mg once daily. In total, 2737 patients were randomized (double-blind) to the treatment with eplerenone or placebo including baseline therapy of diuretics (85%), ACE inhibitors (78%), angiotensin II receptor blockers (19%), beta blockers (87%), anti thrombotic drugs (88%), lipid lowering agents (63%), and digitalis glycosides (27%). The mean LVEF was ~26% and the mean QRS duration was ~122 msec. Most of the patients (83.4%) were previously hospitalized for CV reasons within 6 months of randomization, with around 50% of them due to heart failure. Around 20% of the patients had implantable defibrillators or cardiac resynchronization therapy.The primary endpoint, death from cardiovascular causes or hospitalization for heart failure occurred in 249 patients (18.3%) in the eplerenone group and 356 patients (25.9%) in the placebo group (RR 0.63, 95% CI, 0.54-0.74; p<0.001). The effect of eplerenone on the primary endpoint outcomes was consistent across all pre-specified subgroups.The secondary endpoint of all cause mortality was met by 171 patients (12.5%) in the eplerenone group and 213 patients (15.5%) in the placebo group (RR 0.76; 95% CI, 0.62-0.93; p = 0.008). Death from CV causes was reported in 147 (10.8%) patients in the eplerenone group and 185 (13.5%) patients in the placebo group (RR 0.76; 95% CI, 0.61-0.94; p = 0.01).During the study, hyperkalaemia (serum potassium level > 5.5 mmol/L) was reported in 158 patients (11.8%) in the eplerenone group and 96 patients (7.2%) in the placebo group (p < 0.001). Hypokalaemia, defined as serum potassium levels < 4.0 mmol/L, was statistically lower with eplerenone when compared to placebo (38.9% for eplerenone compared to 48.4% for placebo, p<0.0001).