A Study to Test Whether ZS (Sodium Zirconium Cyclosilicate) Can Reduce the Incidence of Increased Blood Potassium Levels Among Dialized Patients.

Inclusion Criteria

• Provision of informed consent prior to any study specific procedures
• Female or male aged ≥ 18 years at screening Visit 1. For patients aged 5.4 mmol/L after long inter-dialytic interval and >5.0 mmol/L after one short inter-dialytic interval during screening (as assessed by central lab).
• Prescribed dialysate K concentration ≤ 3 mmol/L during screening
• Sustained Qb ≥200 ml/min and spKt/V ≥1.2 (or URR ≥ 63) on stable hemodialysis/hemodiafltration prescription during screening with prescription (time, dialyzer, blood flow [Qb], dialysate flow rate [Qd] and bicarbonate concentration) expected to remain unchanged during study
• Heparin dose (if used) must be stable during screening and expected to be stable during the study
• Subjects must be receiving dietary counseling appropriate for ESRD patients treated with hemodialysis/hemodiafiltration as per local guidelines, which includes dietary potassium restriction.

Exclusion Criteria

• Involvement in the planning and/or conduct of the study (applies to both AstraZeneca, including ZS Pharma staff and/or staff at the study site)
• Hemoglobin 20× 10^9/L) or thrombocytosis (≥450 × 10^9/L) during screening
• Polycythemia (Hb >14 g/dL) during screening
• Diagnosis of rhabdomyolysis during the 4 weeks preceding randomization
• Patients treated with lactulose, xifaxan (rifaximin) or other non-absorbed antibiotics for hyperammonemia within 7 days prior to the first dose of study drug
• Patients unable to take oral ZS drug mix
• Scheduled date for living donor kidney transplant
• Patients with a life expectancy of less than 6 months
• Female patients who are pregnant or breastfeeding
• Females of childbearing potential, unless using contraception as detailed in the protocol or sexual abstinence.
• Known hypersensitivity or previous anaphylaxis to ZS or to components thereof
• Participation in another clinical study with an investigational product during the last 1 month before screening
• Any medical condition, including active, clinically significant infection, that in the opinion of the investigator or Sponsor may pose a safety risk to a patient in this study, which may confound safety or efficacy assessment and jeopardize the quality of the data, or may interfere with study participation
• Presence of cardiac arrhythmias or conduction defects that require immediate treatment
• History of alcohol or drug abuse within 2 years prior to randomization
• Previous randomization in the present study