Busulfan Injection and Metronidazole: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Busulfan Injection
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
Increased busulfan exposure and an increased risk of busulfan toxicity
Interaction Deep Dive
Avoid concomitant use of busulfan with metroNIDAZOLE due to increased busulfan exposure and increased risk for busulfan toxicity1. Do not administer metroNIDAZOLE concomitantly with busulfan unless the benefit outweighs the risk. If no therapeutic alternatives exist and metroNIDAZOLE and busulfan must be given concomitantly, monitor busulfan plasma concentrations and for signs of busulfan toxicity, and adjust the dose of busulfan accordingly 12. Closely monitor for myelosuppression resulting in leukopenia, thrombocytopenia, and anemia. Busulfan trough levels increased approximately 80% with the concomitant use of metroNIDAZOLE, therefore, their coadministration is not recommended 3.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of busulfan
Literature reports
1 report — tap to read
a) Busulfan trough levels increased approximately 80% with the concomitant use of metroNIDAZOLE 3.
Common questions
Can I take Busulfan Injection and Metronidazole together?
Increased busulfan exposure and an increased risk of busulfan toxicity Always confirm with your pharmacist or prescriber before making any change.
How serious is the Busulfan Injection and Metronidazole interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
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 Busulfan Injection 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 (3)
- Product Information: PYLERA(R) oral capsules, bismuth subcitrate potassium, metronidazole, tetracycline HCl oral capsules. H2-Pharma, LLC (per FDA), Montgomery, AL, 2025. DailyMed
- Product Information: LIKMEZ(TM) oral suspension, metronidazole oral suspension. Saptalis Pharmaceuticals LLC (per FDA), Hauppauge, NY, 2023. DailyMed
- Product Information: MYLERAN(R) TABLETS, busulfan tablets. GlaxoSmithKline, Research Triangle Park, NC, 2005. DailyMed
Keep reading about Busulfan Injection
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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