Endocrine Abstracts

The diagnosis of primary aldosteronism results in either the surgical cure of hypertension or targeted pharmacotherapy. The two major subtypes of primary aldosteronism are unilateral aldosterone-producing adenoma (APA) and bilateral idiopathic hyperplasia (IHA). Patients with APA are usually treated with unilateral adrenalectomy, and patients with IHA are treated medically. Most patients with primary aldosteronism have IHA and require pharmacotherapy. Because of the recent recognition of aldosterone-dependent cardiovascular toxicity, normalization of circulating aldosterone or aldosterone receptor blockade should be part of the management plan for all patients with primary aldosteronism.

Spironolactone has been the drug of choice to treat primary aldosteronism. However, it is not selective for the aldosterone receptor and side effects include gynecomastia, impotence, and menstrual irregularity. Eplerenone is a new steroid-based antimineralocorticoid, which acts as a competitive and selective aldosterone receptor antagonist. In September, 2002, eplerenone was approved by the US Federal Drug Administration for the treatment of hypertension. The 9,11-epoxide group in eplerenone results in a significant reduction of the molecule?s progestational and antiandrogenic actions compared to spironolactone; eplerenone has 0.1% of the binding affinity to androgen receptors and <1% of the binding affinity to progesterone receptors compared to spironolactone. The effectiveness of eplerenone in the treatment of mild to moderate essential hypertension has been demonstrated. The doses used ranged from 50 to 400 mg once daily. Eplerenone was well tolerated with the incidence of adverse events similar to placebo. Treatment trials comparing the efficacy of eplerenone vs. spironolactone for the treatment of primary aldosteronism have not been published. Presumably eplerenone will be the superior drug if it is shown to be as effective as spironolactone for the treatment of mineralocorticoid-dependent hypertension and if it lacks the limiting antiandrogen side effects of spironolactone.