Disulfiram and Warfarin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Warfarin
Disulfiram
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased warfarin exposure, an increased risk of bleeding and an increased INR
Interaction Deep Dive
Concomitant use of warfarin (CYP1A2 substrate) and disulfiram (CYP1A2 inhibitor) may increase warfarin exposure and may also increase INR. Consider the CYP1A2 inhibition potential when starting, stopping, or changing dose of concomitant medications. Closely monitor INR if concomitant disulfiram is used with warfarin3. Concomitant disulfiram and warfarin therapy has resulted in a potentiation of warfarin's hypoprothrombinemic effect. Disulfiram may augment the anticoagulant effect of warfarin by directly affecting the hepatic mechanism responsible for hypoprothrombinemia 4.
Why it happens (mechanism)
Inhibition of CYP1A2-mediated metabolism of warfarin
Literature reports
3 reports — tap to read
a) The effects of concomitant warfarin and disulfiram were studied in seven subjects who served as their own controls. The AUC of one-stage prothrombin times for the S-enantiomer of warfarin increased by 67% when both drugs were given compared to S-warfarin alone. No change in this measure of hypoprothrombinemic status was seen with the R-enantiomer. Because no change in plasma concentrations of the warfarin enantiomers was seen, it was suggested that the impact of concomitant use of these drugs on hypoprothrombinemia was due to a direct effect of disulfiram on the hepatic mechanism responsible for hypoprothrombinemia. Further study is needed 4.
b) A controlled clinical trial was conducted evaluating the concomitant use of these two drugs in 8 healthy volunteers. Patients served as their own controls and received warfarin as a single large dose (1.5 mg/kg) or over 21 days as 15 mg for three days followed by a maintenance dose of 7 mg daily. Patients received warfarin alone or in combination with disulfiram. With concurrent administration, an increase in the plasma level and hypoprothrombinemic effect of warfarin was noted in seven patients with the single dose and in six patients with the 21-day regimen. Disulfiram appeared to inhibit the metabolism of warfarin 1.
c) A case of disulfiram increasing the hypoprothrombinemic effect of warfarin was reported. Adequate anticoagulant therapy was established with warfarin 7.5 and 10 mg on alternate days. When 250 mg daily of disulfiram was added, prothrombin percentages fell and the patient hemorrhaged. A similar response was noted on two other occasions with disulfiram 250 mg every other day 2.
Common questions
Can I take Disulfiram and Warfarin together?
Increased warfarin exposure, an increased risk of bleeding and an increased INR Always confirm with your pharmacist or prescriber before making any change.
How serious is the Disulfiram and Warfarin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Disulfiram or Warfarin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (4)
- O'Reilly RA: Interaction of sodium warfarin and disulfiram (Antabuse) in man. Ann Intern Med 1973; 78:73. PubMed
- Rothstein E: Warfarin effect enhanced by disulfiram (letter). JAMA 1968; 206:1574-1575. PubMed
- Product Information: WARFARIN SODIUM oral tablets, warfarin sodium oral tablets. Teva Pharmaceuticals (per Dailymed), Parsippany, NJ, 2023. DailyMed
- O'Reilly RA: Dynamic interaction between disulfiram and separated enantiomorphs of racemic warfarin. Clin Pharmacol Ther 1981; 29:332-336. PubMed
Keep reading about Warfarin
Keep reading about Disulfiram
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