Drug Safety Communication from FDA: Requires Drug Interaction Studies for Kayexalate (sodium polystyrene sulfonate)

On October 22, 2015, the Food and Drug Administration (FDA) issued a safety alert that it is requiring the Kayexalate manufacturer to conduct studies to investigate Kayexalate’s potential to bind to other medications administered by mouth – drug interactions that could affect how well the other medications work. The approved labeling for Kayexalate describes its potential to decrease absorption of lithium and thyroxine; however, extensive drug-drug interaction studies with Kayexalate have not been performed. During the FDA’s review of another potassium-lowering drug, the drug was found to bind to about half of the medications tested, some of which are commonly used in patients who require potassium-lowering drugs. Such binding could decrease the effects of these medications.

Background: Kayexalate (sodium polystyrene sulfonate) is used to treat hyperkalemia, a serious condition in which the amount of potassium in the blood is too high. It works by binding potassium in the large intestine so it can be removed from the body.

Recommendation: Prescribers and patients should consider separating Kayexalate dosing from other medications taken by mouth by at least 6 hours. Health care professionals should monitor blood levels or clinical response to the other medications when appropriate. Patients should not stop taking their potassium-lowering drugs without talking to their health care professional.

Go to the FDA Safety Alert