Long-term efficacy of oral calcium polystyrene sulfonate for treating hyperkalemia in CKD Patients

Abstract

Background Previously, sodium polystyrene sulfonate (SPS) was used to treat hyperkalemia in patients with chronic kidney disease (CKD). However, it is no longer prescribed because of a poor side-effect profile and uncertain efficacy. Recently, new agents for treatment of hyperkalemia such as patiromer and sodium zirconium cyclosilicate are emerging for the treatment of hyperkalemia. In contrast, calcium polystyrene sulfonate (CPS) has been widely used for patients with advanced CKD in Asia including South Korea. However, its efficacy and adverse events are yet to be elucidated. This study was undertaken to investigate the long-term efficacy of oral CPS for treating mild hyperkalemia (≥5.0 mEq/L) on an outpatient basis. Methods A retrospective analysis was done using electronic medical records. Adult (> 18 years old) patients were enrolled who visited our outpatient department due to CKD. They took oral CPS for 1 week or more because of their elevated serum potassium levels > 5.0 mmol/L. We evaluated only the periods with a fixed dosage of CPS and divided patients into 4 groups. Those with medication periods of less than 3 months, ≤3 and < 6 months, ≤6 and < 12 months, and 1 year or more were Group 1, 2, 3, and 4, respectively. The response was defined as a decrease in the serum potassium level (> 0.1 mmol/L) after the treatment with CPS.

Results A total of 247 patients were enrolled, and 136 (55.1%) were male. The mean (±SD) age was 64 (± 14) years. The eGFR was 30 ± 15 mL/min/1.73 m2. As the stage of CKD progresses, serum hemoglobin and total CO2 level decreased (P<0.001) without changes in serum sodium and potassium levels. The basal serum potassium level was 5.8 ± 0.3 mmol/L. CPS was used at a daily dose of 8.0 ± 3.6 g/d for 5.6 ± 8.7 months. Angiotensin converting enzyme inhibitors or angiotensin receptor blockades (ACEIs/ARBs) were used in 155 patients (63%). When all patients were taken together, the serum potassium level was significantly decreased. CPS was used at a daily dose of 7.6 ± 3.6 g/d for 23.1 ± 10.5 months. Response rates were 87%, 74%, 90% and 90% for Group 1, Group 2, Group 3, and Group 4, respectively. Compared with non-responders, the serum potassium levels in responders were more elevated. Over the whole period of follow-up, no serious adverse events were reported. Constipation was noted in 19 patients (8%).

Conclusions A small dose of oral calcium polystyrene sulfonate is effective and safe for controlling mild hyperkalemia in patients with CKD over a long period of time.