Cholestyramine with Warfarin Interaction Details

Brand Names Associated with Cholestyramine

Brand Names Associated with Warfarin

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Feb 28, 2024

Interaction Effect

Decreased effects of warfarin

Interaction Summary

Cholestyramine has been shown to decrease the absorption and may interrupt the enterohepatic recirculation of warfarin, phenprocoumon, and dicumarol resulting in a reduced anticoagulant effect[1][2][3][4][5].

Severity

Moderate

Onset

Delayed

Evidence

Probable

How To Manage Interaction

Monitor the International Normalized Ratio (INR) whenever cholestyramine is added to or discontinued during co-treatment with warfarin or whenever cholestyramine dose is changed during concomitant therapy. Dose timing adjustments may not adequately prevent the interaction.

Mechanism Of Interaction

Decreased warfarin absorption, interference with enterohepatic recirculation

Literature Reports

A) Six healthy subjects were studied to determine the significance of cholestyramine interaction with warfarin [6]. Cholestyramine 12 g (administered in 3 divided doses) was added to warfarin 40 mg. The interaction was tested in two ways: 1) cholestyramine 4 g was given concomitantly with the warfarin dose and the other 2 cholestyramine doses at successive 3 hour intervals, and 2) cholestyramine 4 g was given 3 hours before the warfarin dose and 3 and 6 hours after the warfarin dose. It was noted that cholestyramine significantly (p greater than 0.01) decreased plasma warfarin concentration for both concomitant and remote administration when compared to control values. It was postulated that little binding of warfarin by cholestyramine occurs in the acid stomach, but, when warfarin enters the small bowel, it is converted to its anionic form which would promote binding, thereby making it unavailable for absorption [6].

References

1 ) Meinertz T, Gilfrich MJ, Bork R, et al: Treatment of phenprocoumon intoxication with cholestyramine. Br Med J 1977; 2:439.

2 ) Jahnchen E, Meinertz T, Gilfrich HJ, et al: Enhanced elimination of warfarin during treatment with cholestyramine. Br J Clin Pharmacol 1978; 5:437-440.

3 ) Koch-Weser J & Koch-Weser J: Drug interactions in cardiovascular therapy. Am Heart J 1975; 90:93-116.

4 ) Koch-Weser J & Sellers EM: Drug interactions with coumarin anticoagulants (part 2). N Engl J Med 1971; 285:547-558.

5 ) Harvengt C & Desager JP: Effect of colestipol, a new bile acid sequestrant, on the absorption of phenprocoumon in man. Eur J Clin Pharmacol 1973; 6:19-21.

6 ) Robinson DS, Benjamin DM, & McCormick JJ: Interaction of warfarin and nonsystemic gastrointestinal drugs. Clin Pharmacol Ther 1971; 12:491-495.

Cholestyramine Overview

• Cholestyramine is used with diet changes (restriction of cholesterol and fat intake) to reduce the amount of cholesterol and certain fatty substances in your blood. Accumulation of cholesterol and fats along the walls of your arteries (a process known as atherosclerosis) decreases blood flow and, therefore, the oxygen supply to your heart, brain, and other parts of your body. Lowering your blood level of cholesterol and fats may help to prevent heart disease, angina (chest pain), strokes, and heart attacks.

• This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Warfarin Overview

• Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechanical) heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis (swelling and blood clot in a vein) and pulmonary embolism (a blood clot in the lung). Warfarin is in a class of medications called anticoagulants ('blood thinners'). It works by decreasing the clotting ability of the blood.

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Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.

Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.

Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.

Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.

Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.

Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.

How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.

Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.

Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.