Sodium polystyrene sulfonate (sold under the brand names SPS, Kayexalate, and Kionex) is widely used for treatment of hyperkalemia. It is a synthetic cation-bound resin that exchanges sodium cations for potassium in the gastrointestinal (GI) lumen, resulting in increased fecal potassium excretion that in turn leads to decreased serum potassium levels. This drug was first introduced for treatment of hyperkalemia in 2 small uncontrolled case series in the early 1950s, and the US Food and Drug Administration (FDA) approved it for the short-term treatment of hyperkalemia in 1958.