LONG-TERM EFFICACY OF ORAL CALCIUM POLYSTYRENE SULFONATE FOR TREATING HYPERKALEMIA IN CKD PATIENTS

Abstract

Introduction and Aims: Whereas new agents treating hyperkalemia such as patiromer and sodium zirconium cyclosilicate are emerging, calcium polystyrene sulfonate (CPS) has been widely used for patients with advanced chronic kidney disease (CKD) in South Korea. However, its efficacy and adverse effects are yet to be reported. This study was undertaken to investigate the long-term efficacy of oral calcium polystyrene sulfonate for treating mild hyperkalemia on an outpatient basis.

Methods: Patients were enrolled who visited our outpatient department due to CKD from January 2010 to December 2014 and took oral CPS for 1 week or more because of their elevated serum potassium levels ≥ 5.0 mmol/L. They continued a fixed dosage of CPS during their medication; Medication periods of less than 3 months, 3 to 6 months, 6 months to 1 year, and 1 year or more were defined as Phase 1, 2, 3, and 4, respectively. Two different formulae, granules (Kalimate®) and jelly (Argamate®), were prescribed according to patient preference.

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, ranging from 5 to 85 mL/min/1.73 m2. Underlying kidney diseases were diabetic nephropathy (45%), hypertensive nephrosclerosis (22%), chronic glomerulonephritis (14%), and others. The basal serum potassium level was 5.8 ± 0.3 mmol/L. Kalimate® and Argamate® were given to 172 and 75 patients, respectively. Angiotensin converting enzyme inhibitors (ACEIs) or angiotensin receptor blockades (ARBs) was used in 155 patients (63%). In Phase 1 (n=234), serum potassium was lowered from 5.8 ± 0.3 mmol/L to 4.9 ± 0.6 mmol/L (P < 0.001). CPS was used at a daily dose of 8.0 ± 3.5 g/d for 7.5 ± 5.4 weeks. Responders were 210 patients (90%) when positive response was defined as a decrease in serum potassium over the period of Phase 1. The response was associated neither with use of ACEIs/ARBs (n=145) nor with discontinuance of ACEIs/ ARBs (n=7). Notably, most of the patients (138/145) maintained ACEIs/ARBs during Phase 1. In Phase 2 (n=98), serum potassium was lowered from 5.7 ± 0.3 mmol/L to 4.9 ± 0.6 mmol/L (P < 0.001). CPS was used at a daily dose of 7.5 ± 3.5 g/d for 4.9 ± 0.6 months. In Phase 3 (n=68), serum potassium was lowered from 5.7 ± 0.3 mmol/L to 5.0 ± 0.5 mmol/L (P < 0.001). CPS was used at a daily dose of 8.0 ± 3.5 g/d for 10.2 ± 1.8 months. In Phase 4 (n=38), serum potassium was lowered from 5.7 ± 0.3 mmol/L to 4.7 ± 0.6 mmol/L (P < 0.001). CPS was used at a daily dose of 7.5 ± 3.5 g/d for 23.1 ± 10.5 months. Response rates were 87%, 91%, and 90% in Phase 2, Phase 3, and Phase 4, respectively. Over the whole follow-up periods, no serious adverse effects 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.