The Food and Drug Administration (FDA) is recommending that patients avoid the concomitant use of sodium polystyrene sulfonate with other oral medications. 

Sodium polystyrene sulfonate, a cation exchange resin, is indicated to treat hyperkalemia and is available as the brand Kayexalate (Concordia), as generic brands (Kalexate, Kionex, SPS), and non-branded generics. It binds with potassium in the intestines so it can be cleared from the body. 

In an in vitro study, Kayexalate was evaluated with six oral medications commonly administered together: amlodipine, metoprolol, amoxicillin, furosemide, phenytoin, and warfarin. The data showed significant binding of these drugs to sodium polystyrene sulfonate, decreasing the absorption and efficacy of the agents. 

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As a result, the FDA is recommending that prescription and over-the-counter (OTC) oral medicines should be taken at least three hours before or three hours after taking sodium polystyrene sulfonate. This is based on the anticipated amount of time it would take for either drug to pass through the stomach. For patients with gastroparesis or other conditions causing delayed emptying of food from the stomach, the spacing interval should be increased to at least six hours. 

The drug labeling is being updated to include information about separating the doses. 

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