Disulfiram and Metronidazole: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Disulfiram
Metronidazole
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
An increased risk of psychotic reactions
Interaction Deep Dive
Concurrent use of disulfiram and metroNIDAZOLE has been reported to result in psychotic episodes and confusional states423. Since metroNIDAZOLE alone can cause central nervous system side effects, it is not clear if these results represent a true drug interaction 5. However, metroNIDAZOLE is contraindicated in patients who have used disulfiram within the last two weeks 16.
Why it happens (mechanism)
Unknown
Literature reports
3 reports — tap to read
a) A study administered disulfiram 500 mg daily for one month and then 250 mg daily thereafter to 58 hospitalized chronic alcoholics in a double-blind manner. Twenty-nine patients received metroNIDAZOLE 750 mg daily for one month, which was then reduced to 250 mg daily, and 29 patients received placebo. Six of the 29 patients receiving the disulfiram-metroNIDAZOLE combination developed symptoms of acute psychosis or a confusional state. Patients receiving disulfiram and placebo did not experience these symptoms. None of the subjects were psychotic prior to initiation of therapy and no alcohol was administered. Symptoms were evident between the tenth and fourteenth day of treatment. Following discontinuation of disulfiram and metroNIDAZOLE, symptoms persisted for two to three days. Recovery was evident in one to two weeks 2.
b) A study reported the development of an acute psychotic paranoid reaction in which a patient thought he spoke with God. This was after metroNIDAZOLE 500 mg daily was added to disulfiram 500 mg daily. The patient acquired a new heightened appreciation for colors and sensations. The patient also felt he had a mind-extending religious elevating and enlightening experience 3.
c) No mechanism of action for this drug-drug interaction has been elucidated. It is possible that metroNIDAZOLE may have a synergistic effect with disulfiram, as disulfiram is known to produce a toxic psychosis syndrome 4.
Common questions
Can I take Disulfiram and Metronidazole together?
An increased risk of psychotic reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Disulfiram and Metronidazole interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
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 Metronidazole 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 (6)
- Product Information: LIKMEZ(TM) oral suspension, metronidazole oral suspension. Saptalis Pharmaceuticals LLC (per FDA), Hauppauge, NY, 2023. DailyMed
- Rothstein E & Clancy DD: Toxicity of disulfiram combined with metronidazole. N Engl J Med 1969; 280:1006. PubMed
- Scher JM: Psychotic reaction to disulfiram. JAMA 1967; 201:1051. DOI
- Goodhue WW Jr: Disulfiram-metronidazole (well-identified) toxicity. N Engl J Med 1969; 280:1482. PubMed
- Product Information: Antabuse(R), disulfirm. Wyeth-Ayerst Laboratories, Philadelphia, PA, 1995. DailyMed
- Product Information: FLAGYL(R) 375 oral capsule, metronidazole oral capsule. GD Searle, Chicago, IL, 2005. DailyMed
Keep reading about Disulfiram
Keep reading about Metronidazole
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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