Amiloride noninferior to spironolactone for resistant hypertension

In the treatment of patients with resistant hypertension, amiloride is no better or worse than spironolactone at reducing home systolic blood pressure (SBP) levels, according to a study.

Conducted at 14 sites across South Korea, the study included 118 patients (median age 55 years, 70 percent male) with home SBP of at least 130 mm Hg after a 4-week run-in period, wherein the patients received a fixed-dose triple medication combination (angiotensin receptor blocker, calcium channel blocker, and thiazide).

The patients were randomly assigned to receive 5 mg/day of amiloride (n=58) or 12.5 mg/day of spironolactone (n=60). If home SBP remained ≥130 mm Hg and serum potassium was <5.0 mmol/L after 4 weeks of treatment, dosages were increased to 10 mg/day and 25 mg/day in the amiloride and spironolactone groups, respectively.

At baseline, the mean home SBP was 141.5 mm Hg in the amiloride group and 142.3 mm Hg in the spironolactone groups. Notably, 8.6 percent of patients in the amiloride group and none in the spironolactone group were using alpha-blockers.

The primary endpoint of change in home SBP at week 12 did not significantly differ between the treatment groups. Specifically, home SBP decreased by −13.6 mm Hg with amiloride vs −14.7 mm Hg with spironolactone (between-group difference, −0.68 mm Hg, 90 percent confidence interval [CI], −3.50 to 2.14), establishing the noninferiority of amiloride (noninferiority margin of −4.4 mm Hg for the lower bound of the CI).

For the secondary endpoints, the percentage of patients who achieved home-measured SBP <130 mm Hg was 66.1 percent in the amiloride group and 55.2 percent in the spironolactone group. The corresponding number of those who achieved office-measured SBP <130 mm Hg was 57.1 percent and 60.3 percent. The differences were not significant.

In terms of safety, one patient in the amiloride group experienced hyperkalaemia, which led to treatment discontinuation. There were no reports of gynecomastia in either treatment group.