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Eplerenone (INN) is a steroidal antimineralocorticoid of the spirolactone group that is used as an adjunct in the management of chronic heart failure. It is similar to the diuretic spironolactone, though it is much more selective for the mineralocorticoid receptor in comparison (i.e., does not possess any antiandrogen, progestogen, glucocorticoid, or estrogenic effects), and is specifically marketed for reducing cardiovascular risk in patients following myocardial infarction. By modifying the alternative drug Spironolactone, the new drug was developed in part to avoid undesired androgenic side effects in male patients. Eplerenone is a potassium-sparing diuretic, meaning that it helps the body get rid of water but still keep potassium.

Eplerenone was developed by Pharmacia Corporation, which was acquired by Pfizer in 2002. It was marketed by Pfizer under the trade name Inspra. The US Food and Drug Administration (FDA) approved the drug for sale in the United States in 2002. Eplerenone is currently approved for sale in the US, EU, Netherlands and Japan. Relative to dosage, eplerenone costs an estimated $2.93 per day when treating congestive heart failure and $5.86 per day when treating hypertension.

Heart Failure
Eplerenone is specifically indicated for the reduction of risk of cardiovascular death in people with heart failure and left ventricular dysfunction within 3–14 days of an acute myocardial infarction, in combination with standard therapies and as treatment against hypertension. A variant of the spirolactone group, Eplerenone was developed to contradict the depletion of essential potassium and magnesium levels that are common amongst other mineralocorticoid receptor antagonists. It is a more expensive alternative to spironolactone. The recommended dosage for Eplerenone treating heart failure is 25-50 mg/day, depending on the tolerance of the patient. According to a study comparing both aldosterone blocking agents, the efficacy of Eplerenone over Spironolactone is dependent upon each individual patient.

Hypertension
Eplerenone can be used individually or in combination with other medications to treat hypertension in patients. Dosage ranges from a once daily dose of 50 mg to twice daily 50 mg dosage (no more than 100 mg/day is recommended, as there is no benefit on blood pressure relief). In an 8 week trial with 417 patients with mild to moderate hypertension, Eplerenone significantly decreased systolic and diastolic blood pressure in a dose-dependent man over a dose range of 50, 100 and 400 milligrams per dose. Eplerenone effectively reduces blood pressure compared to agents such as spironolactone, enalapril, losartan and amlodipine, but it's effect on mortality is still generally unknown.

Pharmacology
Eplerenone is an antimineralocorticoid, or an antagonist of the mineralocorticoid receptor (MR). Eplerenone is also referred to chemically as "Pregn-4-ene-7,21-dicarboxylic acid, 9,11-epoxy-17-hydroxy-3-oxo, γ-lactone, methyl ester (7α, 11α,17α), was derived from spironolactone by the introduction of a 9α,11α-epoxy bridge and by substitution of the 17α-thoacetyl group of spironolactone with a carbomethoxy group". The drug controls high blood pressure by binding the aldosterone hormone to the mineralocorticoid receptor (MR) in epithelial tissues, such as the kidney. This helps to increase blood volume and regulate blood pressure. It has 10- to 20-fold lower affinity for the MR relative to spironolactone, and is less potent in vivo as an antimineralocorticoid. However, in contrast to spironolactone, eplerenone has little affinity for the androgen, progesterone, and glucocorticoid receptors. It also has more consistently observed non-genomic antimineralocorticoid effects relative to spironolactone (see membrane mineralocorticoid receptor). Eplerenone differs from Spironolactone in its extensive metabolism, with a short half-life and inactive metabolites.

Adverse effects
Adverse effects of aldosterone treatments occur in non-epithelial tissues, like the heart and brain, due to changes in water retention and excretion of sodium and potassium. Common adverse drug reactions (ADRs) associated with the use of eplerenone include: hyperkalaemia, hypotension, dizziness, altered renal function, and increased creatinine concentration. Eplerenone may have a lower incidence than spironolactone of sexual side effects such as feminization, gynecomastia, impotence, low sex drive and reduction of size of male genitalia. This is because other antimineralocorticoids have structural elements of the progesterone molecule, causing progestogenic and antiandrogenic outcomes. In this aspect, Eplerenone would be preferable to many male patients seeking no sexual side effects. When considering taking these medicines, it is important to note the variations in their ability to offset the nongenomic effects of aldosterone. However, there has been research conducted on the effectiveness of Spironolactone on the transition for transgendered males. Due to the high risk of elevated potassium levels in individuals taking Eplerenone, the United States FDA suggests routine checks on the individual's potassium level to screen for hyperkalemia.

Contraindications
Eplerenone is contraindicated in patients with hyperkalaemia, severe renal impairment (creatinine Cl less than 30 ml/min), or severe hepatic impairment (Child-Pugh score C). The manufacturer of eplerenone also contraindicates ( relative C.I. ) concomitant treatment with ketoconazole, itraconazole or other potassium-sparing diuretics (though the manufacturer still considers taking these drugs to be absolute C.I.) Potential benefits should be weighted against possible risks.

Drug interactions
Eplerenone is primarily metabolised by the cytochrome P450 enzyme CYP3A4. Thus the potential exists for adverse drug interactions with other drugs that induce or inhibit CYP3A4. Specifically, the concomitant use of the CYP3A4 potent inhibitors ketoconazole and itraconazole is contraindicated. Other CYP3A4 inhibitors including erythromycin, saquinavir, and verapamil should be used with caution. Other drugs that increase potassium concentrations may increase the risk of hyperkalaemia associated with eplerenone therapy, including salt substitutes, potassium supplements and other potassium-sparing diuretics.