Potassium-Lowering Medication May Reduce Effectiveness of Other MedicationsOct 26, 2015
Concordia Pharmaceuticals has been directed by the Food and Drug Administration (FDA) to conduct studies of the potassium-lowering drug Kayexalate, because of the drug interactions that may reduce the effectiveness of other medications.
Current label information for Kayexalate (sodium polystyrene sulfonate) mentions the drug's potential to decrease the absorption of lithium, prescribed for the treatment of the mania of bipolar disorder, and thyroxine, for underactive thyroid. But Concordia has not done extensive studies of Kayexalate's interactions with other drugs, either prescription or over-the-counter.
Kayexalate is prescribed for hyperkalemia, a serious, possibly life-threatening, condition in which the individual has a too-high level of potassium in the blood. Hyperkalemia can cause nausea, muscle fatigue, weakness, paralysis, and abnormal heart rhythms, and the symptoms can be severe enough to be life threatening. Kayexalate and the generics Kionex and SPS work by binding potassium in the large intestine so it can be excreted by the body. The FDA found that Veltassa (patiromer), another potassium-lowering drug, bound to about half of the medications tested with it. Some of these are medications commonly taken by patients who also take potassium-lowering drugs. The binding could decrease the effects of these medications. Veltassa now 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 taken by mouth. To reduce the potential risk, the FDA suggests physicians advise patients taking Kayexalate not to take it within six hours of taking other oral medications. The recommendation applies to any other medication, whether prescription drugs-antibiotics, blood pressure lowering drugs, blood thinners-or nonprescription drugs like antacids and laxatives. The FDA further recommends that health care professionals monitor blood levels or the patient's clinical response to other medications when appropriate. But the agency cautions patients not to stop taking potassium-lowering medication without first consulting a health care professional.
If studies conducted by Concordia Pharmaceuticals confirm significant interactions between Kayexalate and other medications, the FDA's next step could be a revised label for all sodium polystyrene sulfonate medications to indicate the possibility of this type of drug interaction.
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.