Sodium Polystyrene Sulfonate — sold under brand names like Kayexalate and Kionex — is a widely used medication for treating high potassium levels (hyperkalemia). Like any medication, it comes with potential side effects. Some are mild and manageable, while others require immediate medical attention.

This guide explains what to expect when taking Sodium Polystyrene Sulfonate, which side effects are common, which are serious, and when you should call your doctor or go to the emergency room.

What Is Sodium Polystyrene Sulfonate?

Sodium Polystyrene Sulfonate is a cation-exchange resin that works in your intestines to remove excess potassium from your body. It's prescribed when blood potassium levels are dangerously high — a condition that can cause heart rhythm problems and other serious complications. For a deeper look at how the medication works, see our guide on how Sodium Polystyrene Sulfonate works.

The medication comes as an oral powder you mix with liquid, a pre-mixed oral suspension, or a rectal enema. It's not absorbed into the bloodstream — it works entirely in the gut — but it can still cause side effects.

Common Side Effects

These side effects are relatively common and usually not dangerous, though they can be uncomfortable. Many people experience at least one:

• Nausea — The gritty texture and taste of the suspension can cause nausea, especially when first starting the medication.
• Vomiting — Some people vomit after taking Sodium Polystyrene Sulfonate, particularly at higher doses.
• Constipation — This is one of the most frequently reported side effects. The resin can slow down bowel movements and harden stools.
• Diarrhea — Less common than constipation, but some formulations (especially those previously combined with sorbitol) can cause loose stools.
• Loss of appetite — The medication's taste and GI effects can reduce your desire to eat.
• Stomach irritation or cramping — Mild abdominal discomfort is common, particularly in the first few days.

Most common side effects improve as your body adjusts. If they persist or become bothersome, talk to your doctor — they may adjust the dose or timing.

Serious Side Effects

Sodium Polystyrene Sulfonate can cause serious — and in rare cases, life-threatening — side effects. Know these warning signs:

Intestinal Necrosis (Bowel Injury)

This is the most dangerous potential side effect. The FDA issued a safety warning in 2009 about cases of colonic necrosis (death of bowel tissue), particularly when Sodium Polystyrene Sulfonate was used with sorbitol. Symptoms include:

• Severe abdominal pain
• Bloody stools or rectal bleeding
• Fever
• Abdominal swelling or tenderness

This is a medical emergency. If you experience any of these symptoms, go to the emergency room immediately.

Bowel Obstruction and Fecal Impaction

Severe constipation from the resin can lead to bowel obstruction or fecal impaction. Warning signs include:

• No bowel movements for several days
• Severe bloating and abdominal pain
• Inability to pass gas
• Vomiting

Electrolyte Imbalances

Sodium Polystyrene Sulfonate isn't selective — while it removes potassium, it can also pull out calcium and magnesium. This can cause:

• Hypokalemia (potassium drops too low) — Symptoms include muscle weakness, cramps, irregular heartbeat, and fatigue.
• Hypocalcemia (low calcium) — May cause tingling in hands and feet, muscle spasms, or seizures.
• Hypomagnesemia (low magnesium) — Can cause tremors, muscle twitching, and abnormal heart rhythms.

Your doctor should monitor your electrolyte levels with regular blood tests while you're taking this medication.

Heart-Related Concerns

Both high and low potassium can affect your heart. If Sodium Polystyrene Sulfonate lowers your potassium too much, you may experience:

• Irregular heartbeat or palpitations
• Dizziness or lightheadedness
• Chest discomfort

This is especially important if you take digoxin (Digitalis), because low potassium increases the risk of digitalis toxicity. Let your doctor know about all medications you take. Learn more in our drug interactions guide.

Side Effects in Specific Populations

Elderly Patients

Older adults are at higher risk for constipation and bowel complications from Sodium Polystyrene Sulfonate. Doctors should use the lowest effective dose and monitor bowel function closely.

Patients With Kidney Disease

Ironically, the people who most need Sodium Polystyrene Sulfonate — those with kidney disease — may also be at higher risk for electrolyte imbalances. Frequent lab monitoring is essential.

Neonates

Sodium Polystyrene Sulfonate is contraindicated in neonates (newborns) with reduced gut motility due to the risk of intestinal necrosis.

Pregnant and Breastfeeding Women

Sodium Polystyrene Sulfonate is not absorbed into the bloodstream, so it's generally not expected to harm a developing fetus or pass into breast milk. However, always discuss any medication with your doctor during pregnancy.

How to Manage Side Effects

Here are practical tips for handling common side effects:

• For constipation — Drink plenty of water throughout the day. Ask your doctor about taking a mild stool softener (but avoid sorbitol-containing laxatives). Eat fiber-rich foods that are low in potassium.
• For nausea — Take the medication with a small meal. Mixing the powder with a cold, flavored liquid (not orange juice or potassium-rich drinks) may improve tolerance.
• For stomach cramps — Take the dose at a consistent time and avoid taking it on a completely empty stomach.
• For taste/texture issues — Mix the powder thoroughly. Some patients find it easier to take with apple juice or cranberry juice.

Never stop taking Sodium Polystyrene Sulfonate without talking to your doctor. High potassium is dangerous, and stopping the medication abruptly could cause your levels to spike.

When to Call Your Doctor

Call your doctor if you experience:

• Constipation lasting more than 2-3 days
• Ongoing nausea or vomiting that prevents you from keeping the medication down
• Muscle weakness, cramps, or tingling
• Unusual fatigue or confusion
• Heart palpitations or irregular heartbeat

Go to the ER immediately if you have:

• Severe abdominal pain
• Blood in your stool
• Fever combined with abdominal symptoms
• Seizures
• Severe chest pain or difficulty breathing

Final Thoughts

Sodium Polystyrene Sulfonate is an effective medication for lowering high potassium, but it does come with real side effects — from mild constipation to rare but serious bowel complications. The key is knowing what to watch for and staying in close contact with your healthcare team.

Make sure your doctor monitors your electrolytes regularly, report any new symptoms promptly, and never hesitate to seek emergency care for severe abdominal pain or bleeding.

If you're having trouble finding Sodium Polystyrene Sulfonate at your pharmacy, Medfinder can help you locate it in stock near you. And for more information about this medication, check out What Is Sodium Polystyrene Sulfonate? or our guide to saving money on your prescription.