The aim of this prospective, randomised, open-label, blinded-end point study was to compare the efficacy and safety of
eplerenone versus
spironolactone in patients with bilateral idiopathic
hyperaldosteronism (IHA). After a 2-week washout period, 34 patients with IHA were assigned to receive either
spironolactone 25 mg b.i.d. (n = 17) or
eplerenone 25 mg b.i.d. (n = 17) for 24 weeks. If the patients' blood pressure (BP) was not < 140/90 mmHg, the doses were gradually increased up to 400 mg for
spironolactone and 200 mg for
eplerenone. If the patients' BP remained uncontrolled, a daily dose of
hydrochlorothiazide 12.5 mg was added at week 16. The primary outcome was the percentage of patients with BP < 140/90 mmHg at 16 weeks (i.e., with
aldosterone antagonist monotherapy). The patients' BP was normalised in 13 out of 17 (76.5%) and 14 out of 17 (82.4%) patients in the
spironolactone and
eplerenone groups, respectively (p = 1.00). Systolic BP decreased more rapidly with
eplerenone. Serum
potassium levels were normalised (> 3.5 mmol/l) in all patients at 4 weeks. Mild hyperkalaemia was observed in two patients receiving 400 mg of
spironolactone and in three patients receiving 150 mg of
eplerenone. Two patients presented with bilateral painful gynaecomastia at the end of week 16 while receiving 400 mg of
spironolactone. Switching
spironolactone to 150 mg of
eplerenone daily resulted in resolution of gynaecomastia and also maintained BP control. At the end of the study, 19 patients were on
eplerenone and 15 were on
spironolactone. However, this did not affect the primary end point, because the switch from
spironolactone to
eplerenone (in two patients) occurred at the end of week 16. It was concluded that
eplerenone was as effective as
spironolactone in reducing BP in patients with IHA. The risk of mild hyperkalaemia was similar with both drugs.