Prevalite Side Effects: What to Expect and When to Call Your Doctor

Prevalite — now only available as generic cholestyramine — is a generally safe medication that works entirely in your digestive tract. Because it's not absorbed into your bloodstream, it doesn't have the same types of systemic side effects as many other medications. But it does have a distinctive side effect profile, primarily gastrointestinal, that patients should know about before starting treatment.

Common Side Effects of Cholestyramine (Prevalite)

Most side effects of cholestyramine are gastrointestinal and are more common when you first start taking it or when the dose is increased. The most frequently reported:

• Constipation: The most common side effect. Cholestyramine slows gut transit and can significantly worsen constipation. Your doctor may recommend starting at a low dose and increasing gradually. Adequate fluid intake and dietary fiber can help.
• Bloating and gas (flatulence): Very common, especially in the first few weeks. May improve as your body adjusts.
• Nausea: More common when starting therapy or at higher doses. Taking cholestyramine with food may help.
• Abdominal pain and cramps: Usually mild to moderate; tends to improve after the first few weeks of therapy.
• Heartburn: May occur, particularly if you have a history of acid reflux.
• Vomiting: Less common; usually associated with taking too high a dose too quickly.

Tips to Reduce Common Side Effects

1. Start low, go slow: Begin at one packet or scoop daily before moving to the target dose of 2-4 packets daily.
2. Drink plenty of fluids: Aim for at least 8 glasses of water daily to help prevent constipation.
3. Increase dietary fiber: Fruits, vegetables, and whole grains can help counteract constipation.
4. Take with meals: Mixing cholestyramine in food or taking it during or just after meals can reduce nausea and GI upset.
5. Don't hold it in your mouth: Swallow quickly after mixing to prevent dental enamel exposure.

Serious Side Effects: Call Your Doctor If You Notice These

More serious side effects are less common but important to be aware of:

• Vitamin K deficiency / increased bleeding: Cholestyramine can interfere with absorption of vitamin K. Symptoms include unusual bruising, prolonged bleeding from cuts, or blood in stool/urine. People taking blood thinners (warfarin) are at especially high risk.
• Fat-soluble vitamin deficiency (A, D, E, K): Long-term use can deplete these vitamins. Symptoms may include fatigue, bone pain, vision changes, or muscle weakness. Your doctor may recommend vitamin supplements.
• Increased triglycerides: Cholestyramine can raise triglyceride levels, especially in patients who already have elevated triglycerides. Get a follow-up lipid panel 4-6 weeks after starting therapy. If triglycerides exceed 400 mg/dL, cholestyramine should be discontinued.
• Hyperchloremic acidosis: Rare, but can occur, particularly in patients with kidney disease. Symptoms include fatigue, rapid breathing, nausea, and confusion. This is a medical emergency.
• GI obstruction: Very rare. Taking dry cholestyramine powder without adequate liquid increases the risk of intestinal obstruction. Always mix with at least 2-6 oz of liquid before swallowing.

When Should I Call My Doctor?

Call your doctor promptly if you experience:

• Unusual bruising, prolonged bleeding, or blood in stool/urine
• Severe constipation that doesn't respond to fluids and fiber
• Rapid breathing, extreme fatigue, or confusion
• Symptoms of vitamin deficiency (bone pain, vision changes, muscle weakness)
• New or worsening abdominal pain

Side effects can be more complex if you take other medications alongside cholestyramine. For details on which drugs interact with Prevalite, see our guide on

Prevalite drug interactions.