AUDIENCE: Internal Medicine, Nephrology, Cardiology
ISSUE: FDA is requiring the sodium polystyrene sulfonate (Kayexalate) manufacturer to conduct studies to investigate sodium polystyrene sulfonate's potential to bind to other medications administered by mouth - drug interactions that could affect how well the other medications work.
The approved labeling for sodium polystyrene sulfonate describes its potential to decrease absorption of lithium and thyroxine; however, extensive drug-drug interaction studies with sodium polystyrene sulfonate have not been performed. During FDA's review of another potassium-lowering drug, patiromer (Veltassa), we found that patiromer 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 label for patiromer contains a warning not to take other orally administered medications within 6 hours of taking patiromer.
Similar to patiromer, sodium polystyrene sulfonate may also bind to other medications administered by mouth. To reduce this potential risk, prescribers and patients should consider separating sodium polystyrene sulfonate 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.
If the studies conducted by the sodium polystyrene sulfonate manufacturer, Concordia Pharmaceuticals, confirm significant interactions with other medications, FDA will require all manufacturers of sodium polystyrene sulfonate products to update the drug labels to include information about these drug interactions.
BACKGROUND: Sodium polystyrene sulfonate (Kayexalate) and generic brands Kionex and SPS are used to treat hyperkalemia, a serious condition in which the amount of potassium in the blood is too high. They work by binding potassium in the large intestine so it can be removed from the body.
RECOMMENDATION: Prescribers and patients should consider separating sodium polystyrene sulfonate dosing from other medications taken by mouth by at least 6 hours. Health care professionals should monitor blood levels or clinical response to the other medications when appropriate. Patients should not stop taking their potassium-lowering drugs without talking to their health care professional.
For more information visit the FDA website at: http://www.fda.gov/Safety/MedWatch/SafetyInformation and http://www.fda.gov/Drugs/DrugSafety.
Why is this medication prescribed?
Sodium polystyrene sulfonate is used to treat increased amounts of potassium in the body.
How should this medicine be used?
Sodium polystyrene sulfonate comes as a powder and suspension to take by mouth. It may also be used as a rectal enema. It is usually taken one to four times a day. The powder should be mixed with water or syrup as directed by your doctor. Shake the liquid (suspension) well before each use. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take sodium polystyrene sulfonate exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Sodium polystyrene sulfonate controls high potassium when taken as directed by your doctor. Do not stop taking sodium polystyrene sulfonate without talking to your doctor.
What special precautions should I follow?
Before taking sodium polystyrene sulfonate,
- tell your doctor and pharmacist if you are allergic to sodium polystyrene sulfonate or any other drugs.
- tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially antacids, digoxin, diuretics ('water pills'), laxatives, and vitamins or herbal products.
- tell your doctor if you have or have ever had heart or kidney disease, hypertension, or constipation.
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking sodium polystyrene sulfonate, call your doctor.
- tell your doctor if you are on a sodium-restricted diet.
What special dietary instructions should I follow?
Talk to your doctor before using salt substitutes containing potassium.If your doctor prescribes a low-salt or low-sodium diet, follow these directions carefully.
What should I do if I forget a dose?
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What side effects can this medication cause?
Sodium polystyrene sulfonate may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- upset stomach
If you experience any of the following symptoms, call your doctor immediately:
- muscle weakness
- unusual swelling
- irregular heartbeat
- rectal or lower stomach pain
- increased thirst
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).
What should I know about storage and disposal of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature (unless told otherwise by your pharmacist) and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.If you prepare sodium polystyrene sulfonate from a powder, refrigerate the mixed suspension. Do not use a suspension more than 24 hours after you have prepared it.
What other information should I know?
Keep all appointments with your doctor and the laboratory.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.