A Study Evaluating the Onset-of-Action, Safety, and Efficacy of RDX227675 for the Treatment of Hyperkalemia

Inclusion Criteria: * 18 to 85 years old, inclusive * Two consecutive i-STAT K values ≥ 5.5 to \< 6.5 mmol/L, measured a minimum of 60-minutes apart within 1 day of first RDX227675 dose on Day 1 (prior to randomization) * i-STAT K value ≥ 5.5 to \< 6.5 mmol/L on Day 1 (prior to randomization) * Ability to have repeated blood draws or effective venous catheterization * Females of child bearing potential must have negative urine pregnancy test on Day 1 (prior to randomization) * Females but be non-pregnant, non-lactating, and either be post-menopausal for at least 12 months, have documentation of irreversible surgical sterilization, or confirm the use of one of the acceptable contraceptive methods * Males must agree to use an appropriate method of contraception or have documented surgical sterilization Exclusion Criteria: * Pseudohyperkalemia signs and symptoms * Treatment with K lowering drugs, within 7 days prior to randomization * Uncontrolled Type 2 diabetes, as defined as most recent historical HbA1c \> 10%, or hospitalization to treat hyper- or hypo-glycemia in the past 3 months * Diabetic ketoacidosis * Known hypersensitivity to polystyrene sulfonate * Significant cardiovascular or cerebrovascular events in the past 2 months * Severe heart failure, defined as NYHA (New York Heart Association) class IV or hospitalization to treat heart failure in previous 3 months * History of bowel obstruction, swallowing disorders, severe gastrointestinal disorders, or major gastrointestinal surgery * Major psychiatric disorder (DSM-III-R or DSM-IV) including major depression or other psychoses that has required hospitalization in the last 3 years. History of attempted suicide or uncontrolled bipolar disorder. * Use of an investigational product within 30 days prior to Screening