Comparison of Potassium Adsorbents for Hyperkalemia

Potassium adsorbents play a significant role in managing hyperkalemia, a major complication of chronic kidney disease (CKD). Both calcium polystyrene sulfonate (CPS) and sodium polystyrene sulfonate (SPS) have been shown to lower serum potassium levels, although their effects on mortality and rehospitalization rates have not been examined thoroughly. Meanwhile, sodium zirconium cyclosilicate (SZC) has emerged as a promising new potassium adsorbent.

In a study published in Clinical Kidney Journal, Chikao Onogi, MD, PhD, and colleagues examined how mortality and hyperkalemia-associated hospitalization rates vary with the use of different potassium adsorbents. The retrospective study drew data from a Japanese medical claims database and included data on 36,690,000 patients from 449 hospitals dating from April 2008 to August 2021.

The team identified 924,238 patients with CKD codes and selected those aged ≥20 years. The study enrollees were prescribed potassium adsorbents (SZC, CPS, or SPS) during the 1-year observation period and received consecutive prescriptions for at least 100 days. There were 243 patients receiving SZC; 54,183 receiving CPS; and 18,692 receiving SPS. In each group, 65% to 66% were men and the age range was 72-74 years, with significant differences (P<.001). Hypertension was common in all groups. About half of patients in each group had a history of heart failure (53%, 49%, and 44% in SZC, CPS, and SPS, respectively). The SZC group had a higher percentage of patients on maintenance hemodialysis (46.0% vs 8.2% and 13.0% for CPS and SPS, respectively).

The primary outcome, a composite of mortality and hyperkalemia-associated hospitalization, was lower in the SZC group than in other groups (0.8% for SZC compared with 4.6% and 3.8% for CPS and SPS, respectively). Overall survival rates were >80% during the observation period, and the SZC group had a significantly higher survival rate (P<.001, log-rank test).

The researchers also assessed prescription retention rates for patients prescribed renin-angiotensin-aldosterone system inhibitors (RAASi) at the beginning of the observation period. This was of interest because discontinuing RAASi contributes to increased mortality in patients with CKD. The SZC group had a much higher RAASi prescription continuation rate compared with the SPS group (P=.031). No major differences were found for the other combinations (P=.054 for SZC vs CPS and P=.092 for CPS vs SPS), but the SZC group had a lower discontinuation rate than the CPS group.

Limitations of the study include its retrospective nature and the number of participants, which may have been insufficient. In addition, use of SZC is limited, so the number of deaths and hospitalizations among those using it may not be sufficiently observable. Finally, it would be preferable to include large numbers of patients when assessing discontinuation rates of RAASi to enable a more detailed discussion.

The study’s authors acknowledged that “the high RAASi continuation rate in the SZC group might be a contributing factor for improvement of the primary outcome.” However, they concluded that “this real-world study demonstrated the therapeutic effect of SZC in reducing mortality and hyperkalemia-associated [hospitalizations].”

 Source: Clinical Kidney Journal