Prevalite Drug Interactions: What to Avoid and What to Tell Your Doctor

One of the most important things to know about Prevalite (cholestyramine) is that it has a unique and extensive drug interaction profile. Because it's an anion exchange resin that works in your gut, it can bind to and reduce the absorption of a wide range of other medications you take by mouth. This doesn't mean you can't take other medications — it means the timing of when you take them matters a great deal.

The Golden Rule: Timing Is Everything

Take all other oral medications either 1 hour before or 4–6 hours after your cholestyramine dose. This is the standard recommendation from the FDA and prevents cholestyramine from binding to and reducing absorption of your other drugs. If you take cholestyramine twice daily, plan carefully to create enough separation from your other medications.

High-Risk Drug Interactions to Know About

• Warfarin (Coumadin, Jantoven) — MAJOR: Cholestyramine significantly reduces warfarin absorption, which can lower your anticoagulation level. If you are on warfarin, your INR must be monitored closely when starting or stopping cholestyramine. Take warfarin at least 1 hour before cholestyramine. Conversely, if you stop cholestyramine, warfarin levels can rise — monitor INR and adjust dose accordingly.
• Levothyroxine (Synthroid, Tirosint) — MAJOR: Cholestyramine can bind thyroid hormone replacement medications, significantly reducing their absorption. If you take levothyroxine, take it at least 4 hours before cholestyramine and have your TSH level rechecked 6-8 weeks after starting or stopping cholestyramine.
• Digoxin (Lanoxin) — MAJOR: Cholestyramine can reduce digoxin absorption, potentially lowering blood levels and reducing its effectiveness at controlling heart rhythm or heart failure. Monitor digoxin levels when starting cholestyramine and take digoxin well before cholestyramine.
• Mycophenolate (CellCept, Myfortic) — SERIOUS: Cholestyramine has been shown to significantly reduce mycophenolate levels in transplant patients. This interaction is especially dangerous because inadequate immunosuppression can lead to organ rejection. Use of cholestyramine in transplant patients on mycophenolate should be avoided or very closely monitored.
• Raloxifene (Evista) — SERIOUS: Cholestyramine markedly reduces raloxifene absorption (by up to 90%). Concurrent use is generally not recommended; if unavoidable, separate doses by at least 4-6 hours.

Moderate Interactions: Common Drugs to Space from Cholestyramine

• Diuretics (thiazides, furosemide): Reduced absorption. Take diuretics at least 1 hour before cholestyramine.
• Propranolol (Inderal) and other beta-blockers: Reduced absorption; separate by at least 1 hour.
• Tetracycline antibiotics: Significantly reduced absorption. Take at least 1-2 hours before cholestyramine.
• Penicillin G: Reduced absorption; separate doses appropriately.
• Estrogens and progestins (birth control, hormone therapy): Cholestyramine can reduce absorption of oral hormonal contraceptives. Take hormonal birth control at least 1 hour before cholestyramine or use backup contraception.
• Phenobarbital (seizure medication): Reduced absorption; take phenobarbital well before cholestyramine.
• Fat-soluble vitamins A, D, E, K: Cholestyramine can reduce absorption of these vitamins. If taking vitamin supplements, take them at least 4 hours before or after cholestyramine.

Statins: A Special Consideration

Statins (atorvastatin, pravastatin, lovastatin, simvastatin, fluvastatin) actually have a positive additive interaction with cholestyramine — together they provide better LDL lowering than either drug alone. Evidence shows that combining a statin with cholestyramine can enhance total and LDL cholesterol reduction. However, to avoid absorption issues, take statins at least 1 hour before or 4-6 hours after cholestyramine.

What to Tell Your Doctor and Pharmacist

Before starting cholestyramine, provide your doctor and pharmacist with a complete list of:

• All prescription medications (especially warfarin, thyroid medications, digoxin, immunosuppressants)
• All over-the-counter medications and supplements
• All vitamins and herbal products

Understanding drug interactions goes hand-in-hand with understanding Prevalite's side effects. Read our complete guide on

Prevalite side effects for a full picture.