Sodium polystyrene sulfonate suspension (Kayexalate) is a cation exchange resin used for the reduction of elevated serum potassium. The efficiency of this process in the colon is limited and unpredictable. In vitro this can approach 3 mEq, in vivo one gram of Kayexalate resin/kg should lower serum potassium approximately 1 mEq/L. The action of the medication is to slowly release sodium ions from the resin and replace them with potassium ions as the resin passes through the GI tract or is retained in the colon as an enema. The effect is not immediate and takes 2 to 12 hours after oral administration, longer after rectal administration (Facts and Comparisons, Inc. Drug Facts and Comparisons. Olin, B.R. ed. St. Louis, MO: Facts and Comparisons, Inc; 1996, page 170f). As such, it may not be sufficient to rapidly reduce serious elevations in serum potassium. The resin is not totally selective for potassium; small amounts of magnesium and calcium may also be lost during therapy. If oral route is used, Kayexalate should not be given with antacid. The oral route is more effective in adults. Because of decreased GI motility in neonates, the rectal route is used. If the resin remains in the colon for more than several hours, the colon should be irrigated with a non-sodium containing solution to remove the resin. (Package insert, Roxane Laboratories, Inc. May, 1988.)