Clinicians should advise patients who take sodium polystyrene sulfonate (Kayexalate, Concordia Pharmaceuticals) for hyperkalemia to not take any other oral drugs 3 hours before or after, the US Food and Drug Administration (FDA) announced today.
Separate dosing is advisable, the FDA said, because a study found that sodium polystyrene sulfonate binds to many other orally administered prescription and over-the-counter drugs, decreasing their absorption and effectiveness. The time gap between taking sodium polystyrene sulfonate and other oral drugs should be 6 hours for patients with gastroparesis or other conditions that delay the passage of food from the stomach to the small intestine.
The FDA updated the label for sodium polystyrene sulfonate, available in branded and nonbranded generic forms, in July 2017 to reflect these new dosing recommendations.
Initially approved in 1958, sodium polystyrene sulfonate lowers potassium levels in patients with hyperkalemia by binding to the mineral in the large intestine. Its previous label noted that the drug could decrease the absorption of lithium and thyroxine. Regulatory concern about binding intensified in October 2015, when the FDA approved another potassium binder for hyperkalemia called patiromer (Veltassa, Relypsa). A boxed warning on patiromer’s initial label stated that it should be taken at least 6 hours before or after other oral medications to avoid binding.
The day after patiromer was approved, the FDA announced that it was requiring Concordia Pharmaceuticals to study the potential of sodium polystyrene sulfonate to bind to other oral drugs and reduce their effectiveness. At that time, the agency recommended that prescribers separate the dosing of sodium polystyrene sulfonate from other oral drugs by at least 6 hours.
In November 2016, the FDA revised the label of patiromer to reduce the gap between taking that drug and other oral medications to 3 hours. The boxed warning about binding was removed as well.
The agency based its new dosing recommendations for sodium polystyrene sulfonate on an in vitro study of the binding potential of six oral drugs commonly taken with the treatment for hyperkalemia — amlodipine, metoprolol, amoxicillin, furosemide, phenytoin, and warfarin. “The study found significant binding to sodium polystyrene sulfonate occurred with all of these medicines,” the FDA said in its safety announcement.
More information on today’s announcement about sodium polystyrene sulfonate is available on the FDA’s website.
To report any problems with sodium polystyrene sulfonate, contact MedWatch, the FDA’s safety information and adverse event reporting program, by telephone at 1-800-FDA-1088; by fax at 1-800-FDA-0178; online at http://ift.tt/KHxbBZ; with postage-paid FDA form 3500, available at http://ift.tt/1412xto; or by mail to MedWatch, 5600 Fishers Lane, Rockville, Maryland 20852-9787.
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