Treatment with sodium zirconium cyclosilicate (SZC) led to lasting improvement of hyperkalemia, according to results from an 11-month open-label extension study of the HARMONIZE randomized clinical trial.
SZC selectively binds potassium ions in the colon, reducing absorption and promoting excretion. In the original study, 248 patients with mild hyperkalemia were randomized to SZC or placebo. Within 48 hours, the drug returned potassium to normal and maintained those levels out to 4 weeks.
In the extension study, 123 patients with measured potassium levels of 3.5-6.2 mmol/L, 48 of whom had previously been assigned to placebo, received a 5- to 10-g dose of SZC once per day for up to 337 days. Median daily dose was 10 g, with a dose range of 2.5-15 g (Am J Nephrol. 2019;50[6]:473-480).
Just under 65% of patients completed the 11 months of the open-label extension study, with 88.3% of those achieving the primary endpoint of mean serum potassium levels of 5.1 mmol/L or lower, according to Simon D. Roger, MD, a nephrologist based in Gosford, Australia, and colleagues.
Most patients (83) were taking renin–angiotensin–aldosterone system inhibitors at baseline of the extension study; 78.3% continued a stable dose throughout the open-label phase, 8.4% increased the dose, and 3.6% discontinued.
Two-thirds of patients reported adverse events, most commonly gastrointestinal disorders (18.7%). Constipation was the most frequent (5.7%), followed by nausea, vomiting, and diarrhea (3.3% each).
Adverse events that occurred in 5% or more of participants included hypertension (12.2%), urinary tract infection (8.9%), and peripheral edema (8.1%). Hypertension severity was either mild (46.7%) or moderate (53.3%), and only one case was believed to be associated with the study medication. Thirteen percent of participants reported a total of 17 SMQ edema events. Eleven of the 16 patients had baseline risk factors for edema, leading the authors to conclude that causality between SZC and edema could not be established.
Serious adverse events occurred in 19.5% of participants, and 4.9% of participants discontinued SZC as a result.
SZC is approved for the treatment of hyperkalemia in the United States and Europe. The study was funded by AstraZeneca.
SOURCE: Roger S et al. Am J Nephrol;2019:50(6):473-80.