FDA Asks for Drug Interaction Studies on Kayexalate

Megan Brooks

Disclosures

October 22, 2015

The US Food and Drug Administration (FDA) has asked the maker of sodium polystyrene sulfonate (Kayexalate), Concordia Pharmaceuticals, to conduct studies of the drug's potential to interact with other oral medications, which could affect efficacy.

Kayexalate (and generic brands Kionex and SPS) is a potassium binder used to treat hyperkalemia.

"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," the FDA said in a safety communication posted on its website today.

The action stems from the FDA's recent review of another potassium-lowering drug, patiromer (Veltassa, Relypsa), which was approved yesterday.

During the Veltassa review, the FDA noted that the drug bound 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."

The Veltassa label includes a warning not to take other orally administered medications within 6 hours of taking patiromer.

Similar to Veltassa, Kayexalate may also bind to other oral medications, the FDA cautions.

"To reduce this potential risk, prescribers and patients should consider separating Kayexalate dosing from other medications taken by mouth by at least 6 hours. This includes both prescription medications, such as antibiotics, blood pressure lowering agents and blood thinners, and those purchased over-the-counter without a prescription, such as antacids and laxatives. Health care professionals should monitor blood levels or clinical response to the other medications when appropriate," they advise.

If the studies conducted by Concordia Pharmaceuticals confirm significant interactions between Kayexalate and 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 agency said.

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