Sodium zirconium cyclosilicate (ZS-9) treatment in patients with serum potassium >6.5 mEq/L.

This paper has been commented by Paras Karmacharya et al. Please read the response here.

I am writing in regards to an inaccuracy in the recent case report published in the Journal of Community Hospital Internal Medicine Perspectives by Karmacharya et al. (1). The authors had stated that sodium zirconium cyclosilicate (ZS-9) along with patiromer sorbitex calcium (patiromer) has not been studied in patients with serum potassium (K+) concentrations >6.5 mEq/L. However, it should be noted that while it is true that the phase III trial of patiromer did not include patients with serum K+ >6.5 mEq/L, that is not the case with ZS-9. Specifically, we would like to point out that:

There was no upper limit of baseline serum K+ specified for patient inclusion in the ZS-9 HARMONIZE study (2).

The HARMONIZE study included nine patients with baseline serum K+ >6.5 mEq/L (up to 7.2 mEq/L).

The mean baseline serum K+ of HARMONIZE study patients was 5.6 mEq/L (2).

A Letter to the Editor published in the New England Journal of Medicine described analyses conducted on a combined cohort of 45 patients with baseline serum K+ from 6.1 to 7.2 mEq/L from two Phase III ZS-9 studies (ZS003 and HARMONIZE) (3). The mean baseline serum K+ concentration of this combined cohort was 6.3 mEq/L.

With these data in mind, I affirm to the reader that there are published clinical data of ZS-9 treatment achieving normokalemia in patients with baseline serum K+ >6.5 mEq/L.