May 23 2022

Active ingredient: oral anticoagulants

In case of chronic alcohol consumption, decreases anticoagulant effect due to increase metabolism of oral anticoagulants.

In case of acute alcohol ingestion, the effect is the opposite: increased anticoagulant effect by metabolic inhibition[2][3].

Taking alcohol repeated times in small or moderate amounts , can increase anticoagulant effect[4].

Some studies suggest that alcohol can displace the binding of warfarin to plasma proteins. This phenomena may alter the pharmacokinetics of th? anticoagulant[5].

It is advisable that patients avoid taking alcohol in any amount while they are under treatment with anticoagulants both oral or parenteral, as it can result in hemorrhagic phenomena, especially when are concurrently using other medicines.

In a study on a small group of patients with alcohol dependence, a week after cessation of alcohol consumption, was detected an increase of plasmatic free fraction of warfarin by 19% (p <0.05).

The study's authors call the attention to the possibility that they may present clinically important changes in the anticoagulant effect resulting from changes in the proportion of free drug in the intervals between doses, due to fluctuations this fraction, although the mean free drug concentration remains unchanged[6].


1: Kater RM, Roggin G, Tobon F, Zieve P, Iber FL. Increased rate of clearance of drugs from the circulation of alcoholics. Am J Med Sci. 1969 Jul;258(1):35-9.
2: Tatsumi A, Ikegami Y, Morii R, Sugiyama M, Kadobayashi M, Iwakawa S. Effect of ethanol on S-warfarin and diclofenac metabolism by recombinant human CYP2C9.1. Biol Pharm Bull. 2009 Mar;32(3):517-9.
3: Dreisbach, R.H. Handbook of Poisoning. 12th ed. Norwalk, CT: Appleton and Lange, 1987., p. 171.
4. Havrda DE, Mai T, Chonlahan Enhanced antithrombotic effect of warfarin associated with low-dose alcohol consumption.J.Pharmacotherapy. 2005 Feb;25(2):303-7.
5. Ha CE, Petersen CE, Park DS, Harohalli K, Bhagavan NV.Investigations of the effects of ethanol on warfarin binding to human serum albumin. J Biomed Sci. 2000 Mar-Apr;7(2):114-21.
6. Sandor P, Naranjo CA, Khouw V, Sellers EM. Variations in drug free fraction during alcohol withdrawal.Br J Clin Pharmacol. 1983 Apr;15(4):481-6.