Potassium-Lowering Medication May Reduce Effectiveness of Other Medications: FDA Orders Studies

The Food and Drug Administration (FDA) has directied Concordia Pharmaceuticals, which manufactures the potassium-lowering drug Kayexalate, to investigate Kayexalate’s potential to affect how other medications work.

The FDA’s approved labeling for Kayexalate (sodium polystyrene sulfonate) describes the drug’s potential to decrease the absorption of lithium (for the treatment of the mania of bipolar disorder), and thyroxine (for underactive thyroid). But extensive studies of drug-drug interactions with Kayexalate and other drugs have not been performed, the FDA says.

Kayexalate is for the treatment hyperkalemia, a serious condition in which the level of potassium in the blood is too high. Hyperkalemia can cause nausea, muscle fatigue, weakness, paralysis, and abnormal heart rhythms, and can be life-threatening. Kayexalate and its generics Kionex and SPS work by binding potassium in the large intestine so it can be excreted by the body. The FDA, during its review of the potassium-lowering drug, Veltassa (patiromer), 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 carries a label warning that other oral medications should not be taken within six hours of taking Veltassa.

Kayexalate, like Veltassa, may also bind to other medications that are taken by mouth. To reduce the potential risk, the FDA suggests physicians and patients should consider not taking Kayexalate within six hours of taking other medications orally. The recommendation applies to both prescription medications—antibiotics, blood pressure lowering drugs, blood thinners—and nonprescription drugs like antacids and laxatives. The FDA recommends that health care professionals monitor blood levels or the patient’s clinical response to the other medications when appropriate. But the agency also advises that patients should not stop taking potassium-lowering drugs without discussing this with a health care professional, the FDA says.

If the studies conducted by Concordia Pharmaceuticals confirm significant interactions between Kayexalate and other medications, the FDA’s next step could be to require all sodium polystyrene sulfonate medications to carry revised labels that include information about 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.

 

from Parker Waichman http://www.yourlawyer.com/blog/potassium-lowering-medication-may-reduce-effectiveness-of-other-medications-fda-orders-studies/