Alcohol and Blood Thinners (Warfarin, Pradaxa)

A patient may ask: “I am on warfarin (Coumadin®, Jantoven®).  Is it o.k. for me to drink alcohol?  Does alcohol intake increase the INR?”

Does drinking alcohol change the INR in the patient on warfarin?

Surprisingly little published data exist on the interaction of alcohol and warfarin.  The interaction seems to be complex.

• A review article [ref 1] concluded:
• Intermediate use (2-3 drinks per day) probably does not alter the INR at all.
• Intermittent large amount of alcohol drinking leads to an increase in INR, because the alcohol interferes with warfarin metabolism, i.e. warfarin is metabolized less rapidly. However, this effect may be minimal [ref 2].
• Chronic heavy alcohol intake results in a decreased INR, because the alcohol actually increases the metabolism of warfarin. That means, patients will need more warfarin.
• Individuals who are on warfarin and drink alcohol, even those who drink moderately or heavily, are not more likely going to be over-anticoagulated, i.e. have INRs above 6.0, than individuals who do not drink [ref 3].

Does drinking alcohol increase the risk for bleeding on warfarin?

• The National Institute of Alcohol Abuse and Alcoholism in its “warfarin and alcohol interactions” section makes the sweeping statement  that “occasional drinking may lead to internal bleedin; heavier drinking also may cause bleeding or may have the opposite effect, resulting in possible blood clots” [ref 4].
• A 2011 study showed that patients who drank alcohol (> 20 U of alcohol per week; that equals about 1 ½ liters of wine per week, or 10 pints of beer) and were on warfarin did not have more bleeding [ref  5].

Personal comment

I typically tell patients on warfarin (Coumadin®, Jantoven®) that drinking mild to moderate amounts of alcohol (up to 1-2 glasses of wine or 1-2 beers per day) is probably  safe from a clotting and bleeding point of view and that there is no reason to abstain completely from alcohol while on warfarin.

Pradaxa and Alcohol­

To my knowledge, there is nothing indicating an interaction between alcohol and Pradaxa (dabigatran). The specific resources:

• Pradaxa prescribing information: There is no mention in the FDA-approved summary prescription handout; nothing in the full prescribing information.   
• Official Pradaxa website: “No known dietary restrictions”  European Medicine Agency prescribing information: Nothing mentioned about alcohol.
• British National Health Service: “There are no known interactions between alcohol and Pradaxa

References

1. Buckley NA et al: “Drug interactions with warfarin”. Med J Aust 1992;157:479-483.
2. Mukamal KJ et al. Moderate alcohol consumption and safety of lovastatin and warfarin among men: the post-coronary artery bypass graft trial. Am J Med. 2006;May;119(5):434-440.
3. Hylek EM, Heiman H, Skates SJ, Sheehan MA, Singer DE. Acetaminophen and other risk factors for excessive warfarin anticoagulation. JAMA. 1998;279:657-662.
4. http://pubs.niaaa.nih.gov/publications/Medicine/medicine.htm
5. Lip GY et al.  Comparative validation of a novel risk score for predicting bleeding risk in anticoagulated patients with atrial fibrillation: the HAS-BLED (Hypertension, Abnormal Renal/Liver Function, Stroke, Bleeding History or Predisposition, Labile INR, Elderly, Drugs/Alcohol Concomitantly) score. J Am Coll Cardiol. 2011 Jan 11;57(2):173-180.
6. Penning-van Beest FJA et al: “Lifestyle and diet as risk factors for overanticoagulation”. J Clin Epidemiol 2002;55:411-417.
7. Weathermon R, Crabb DW. Alcohol and medication interactions.Alcohol Res Health. 1999;23:40-54.

Last updated: Oct 26th, 2011

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