Kayexalate, brand of sodium polystyrene sulfonate is a benzene, diethenyl-polymer, with ethenylbenzene, sulfonated, sodium salt. The drug is a cream to light brown finely ground, powdered form of sodium polystyrene sulfonate, a cation-exchange resin prepared in the sodium phase with an in vitro exchange capacity of approximately 3.1 mEq (in vivo approximately 1 mEq) of potassium per gram. The sodium content is approximately 100 mg (4.1 mEq) per gram of the drug. It can be administered orally or in an enema.
As the resin passes along the intestine or is retained in the colon after administration by enema, the sodium ions are partially released and are replaced by potassium ions. For the most part, this action occurs in the large intestine, which excretes potassium ions to a greater degree than does the small intestine. The efficiency of this process is limited and unpredictably variable. It commonly approximates the order of 33 percent but the range is so large that definitive indices of electrolyte balance must be clearly monitored.
Therapeutic group: Medicines for the treatment of hyperkalemia and hyperphosphatemia.
Kayexalate is contraindicated in the following conditions: patients with hypokalemia, patients with a history of hypersensitivity to polystyrene sulfonate resins, obstructive bowel disease, neonates with reduced gut motility (post-operatively or drug induced) and oral administration in neonates
Intestinal Necrosis: Cases of intestinal necrosis, which may be fatal, and other serious gastrointestinal adverse events (bleeding, ischemic colitis, perforation) have been reported in association with Kayexalate use. The majority of these cases reported the concomitant use of sorbitol.
Risk factors for gastrointestinal adverse events were present in many of the cases including prematurity, history of intestinal disease or surgery, hypovolemia, and renal insufficiency and failure. Concomitant administration of sorbitol is not recommended.
• Use only in patients who have normal bowel function. Avoid use in patients who have not had a bowel movement post-surgery.
• Avoid use in patients who are at risk for developing constipation or impaction (including those with history of impaction, chronic constipation, inflammatory bowel disease, ischemic colitis, vascular intestinal atherosclerosis, previous bowel resection, or bowel obstruction).
• Discontinue use in patients who develop constipation.
Serious potassium deficiency can occur from therapy with Kayexalate. The effect must be carefully controlled by frequent serum potassium determinations within each 24 hour period. Since intracellular potassium deficiency is not always reflected by serum potassium levels, the level at which treatment with Kayexalate should be discontinued must be determined individually for each patient. Important aids in making this determination are the patient’s clinical condition and electrocardiogram. Early clinical signs of severe hypokalemia include a pattern of irritable confusion and delayed thought processes.
Like all cation-exchange resins, Kayexalate is not totally selective (for potassium) in its actions, and small amounts of other cations such as magnesium and calcium can also be lost during treatment. Accordingly, patients receiving Kayexalate should be monitored for all applicable electrolyte disturbances.
Systemic alkalosis has been reported after cation-exchange resins were administered orally in combination with non-absorbable cation-donating antacids and laxatives such as magnesium hydroxide and aluminum carbonate. Magnesium hydroxide should not be administered with Kayexalate. One case of grand mal seizure has been reported in a patient with chronic hypocalcemia of renal failure who was given Kayexalate with magnesium hydroxide as laxative
Pregnancy Category C
Animal reproduction studies have not been conducted with Kayexalate. It is also not known whether Kayexalate can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Kayexalate should be given to a pregnant woman only if clearly needed.
It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Kayexalate is administered to a nursing woman.
The effectiveness of Kayexalate in pediatric patients has not been established. In neonates, Kayexalate should not be given by the oral route. In both children and neonates particular care should be observed with rectal administration, as excessive dosage or inadequate dilution could result in impaction of the resin.
Due to the risk of digestive hemorrhage or intestinal necrosis, particular care should be observed in premature infants or low birth weight infants. Rare instances of intestinal necrosis have been reported. Intestinal obstruction due to concretions of aluminum hydroxide, when used in combination with Kayexalate, has been reported.
The following events have been reported from worldwide post marketing experience:
• Fecal impaction following rectal administration, particularly in children;
• Gastrointestinal concretions (bezoars) following oral administration;
• Ischemic colitis, gastrointestinal tract ulceration or necrosis which could lead to intestinal perforation; and,
• Rare cases of acute bronchitis and/or broncho-pneumonia associated with inhalation of particles of polystyrene sulfonate.