Hyperkalemia often limits the use of mineralocorticoid receptor antagonists (MRAs) such as spironolactone in patients with heart failure and CKD. The ongoing REGISTA-K trial, described in the Journal of Cardiac Failure, is exploring whether the potassium binder sodium zirconium cyclosilicate (SZC) can enable safe dose escalation.
REGISTA-K is a multicenter, randomized, double-blind, placebo-controlled study enrolling 266 participants with heart failure with reduced or mildly reduced ejection fraction (HFrEF or HFmrEF) and moderate-to-severe CKD (estimated glomerular filtration rate 15-45 mL/min/1.73 m²). Eligible patients have serum potassium >5.0 mEq/L while on suboptimal spironolactone doses (12.5-37.5 mg). After initial correction of hyperkalemia, participants are randomized 1:1 to receive SZC or placebo across 25 Japanese centers.
The primary endpoint is successful maintenance of a 50 mg/day spironolactone dose at 16 weeks without rescue therapy for hyper- or hypokalemia. By stabilizing potassium levels, SZC may allow patients with concomitant renal dysfunction to achieve optimal MRA dosing, a cornerstone of guideline-directed therapy in heart failure.
