FDA Requires Drug Interaction Studies for Kayexalate

FDA Requires Drug Interaction Studies for Kayexalate

FDA Requires Drug Interaction Studies for Kayexalate


The Food and Drug Administration (FDA) is requiring the manufacturer of the potassium-lowering drug Kayexalate to conduct studies to investigate Kayexalate’s potential to affect how other medications work.

The approved labeling for Kayexalate (sodium polystyrene sulfonate) describes its potential to decrease absorption of lithium (for treating the mania of bipolar disorder) and thyroxine (for underactive thyroid), according to the FDA, though extensive drug-drug interaction studies with Kayexalate and other drugs have not been performed.

Kayexalate treats hyperkalemia, a serious condition in which the amount of potassium in the blood is too high. Kayexalate and the generics Kionex and SPS treat hyperkalemia by binding potassium in the large intestine so it can be removed from the body. During the FDA’s review of another potassium-lowering drug, Veltassa (patiromer), the agency found that Veltassa bound to about half of the medications tested, some of which are commonly taken by patients who require potassium-lowering drugs. Such binding could decrease the effects of these medications. Veltassa contains a label warning not to take other orally administered medications within six hours of taking Veltassa.

Similar to Veltassa, Kayexalate may also bind to other medications taken orally. To reduce this potential risk, prescribers and patients should consider separating Kayexalate dosing from other medications taken by mouth by at least six hours. This advisory includes both prescription medications, such as antibiotics, blood pressure lowering drugs, blood thinners, as well as over-the-counter products like antacids and laxatives. The FDA recommends that health care professionals monitor blood levels or clinical response to the other medications when appropriate. The FDA said that patients should not stop taking their potassium-lowering drugs without discussing this with a health care professional.

If the studies conducted by Concordia Pharmaceuticals, Kayexalate’s manufacturer, confirm significant interactions with other medications, the FDA will require all manufacturers of sodium polystyrene sulfonate products to update the drug labels to include information about these drug interactions.

The FDA encourages health care professionals and patients to report adverse events or side effects related to the use of Kayexalate to the FDA’s MedWatch Safety Information and Adverse Event Reporting Program: www.fda.gov/medwatch/report.htm.

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