Metronidazole Vaginal and Phenprocoumon: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Metronidazole Vaginal
Phenprocoumon
No brand names on record
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 bleeding
Interaction Deep Dive
Concomitant use of metroNIDAZOLE and oral coumarin anticoagulants may result in an increased risk of bleeding due to potentiation of the anticoagulant effect of coumarin anticoagulants and prolongation of prothrombin time. In patients receiving concomitant oral anticoagulant therapy and metroNIDAZOLE, closely monitor the prothrombin time and INR1. Oral metroNIDAZOLE has been reported to inhibit warfarin metabolism and may be capable of affecting other coumarin anticoagulants as well, resulting in an enhanced anticoagulant effect 3. Because the maximum concentration (Cmax) of topically administered metroNIDAZOLE is approximately 1% of values seen with oral administration, this interaction is less likely to occur with topical metroNIDAZOLE administration 2.
Why it happens (mechanism)
Reduced phenprocoumon metabolism
Literature reports
2 reports — tap to read
a) Oral metroNIDAZOLE has been reported to inhibit warfarin metabolism and may be capable of affecting other coumarin anticoagulants as well, resulting in an enhanced anticoagulant effect 3.
b) Because the maximum concentration (Cmax) of topically administered metroNIDAZOLE is approximately 1% of values seen with oral administration, this interaction is less likely to occur with topical metroNIDAZOLE administration 2.
Common questions
Can I take Metronidazole Vaginal and Phenprocoumon together?
An increased risk of bleeding Always confirm with your pharmacist or prescriber before making any change.
How serious is the Metronidazole Vaginal and Phenprocoumon 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Metronidazole Vaginal or Phenprocoumon 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 (3)
- Product Information: LIKMEZ(TM) oral suspension, metronidazole oral suspension. Saptalis Pharmaceuticals LLC (per FDA), Hauppauge, NY, 2023. DailyMed
- Product Information: Noritate(R) topical cream, metronidazole topical cream. Bausch Health US, LLC (per DailyMed), Bridgewater, NJ, 2020. DailyMed
- Product Information: FLAGYL ER(R) oral extended-release tablets, metronidazole oral extended-release tablets. Pfizer (per FDA), New York, NY, 2023. DailyMed
Keep reading about Metronidazole Vaginal
Keep reading about Phenprocoumon
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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