Busulfan Injection and Rifampin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Rifampin
Busulfan Injection
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
Reduced busulfan exposure
Interaction Deep Dive
Concomitant administration of busulfan with rifampin (a CYP3A inducer) can result in subtherapeutic busulfan concentrations, as described in a patient case report1. Busulfan therapeutic drug monitoring is recommended due to busulfan's narrow therapeutic index, pharmacokinetic interactions, and potential inter-patient variability 2.
Why it happens (mechanism)
Induction of CYP3A-mediated metabolism of busulfan
Literature reports
1 report — tap to read
a) A 61-year-old female patient diagnosed with acute myeloid leukemia (AML) and a history of hypothyroidism, dyslipidemia, GERD, and triple negative breast cancer received a conditioning regimen of fractionated busulfan, fludarabine, and post-transplant cyclophosphamide, in addition to prophylactic medications which included rifampin 600 mg daily for tuberculosis prophylaxis. Following the first dose of busulfan 1.76 mg/kg, the elimination half-life was more rapid than expected, with a lower AUC exposure than expected, so the next 2 doses were increased to 2.56 mg/kg/dose. AUC exposure continued to be lower than expected, with a higher elimination half-life as well, despite busulfan being administered with fludarabine, which can delay busulfan clearance. Dose 5 of busulfan was increased again to 2.8 mg/kg, and dose 6 was increased to 2.91 mg/kg after similar AUC and elimination half-life results were obtained. Investigators concluded that rifampin induced CYP3A-mediated metabolism of busulfan, resulting in subtherapeutic busulfan concentrations 1.
Common questions
Can I take Busulfan Injection and Rifampin together?
Reduced busulfan exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Busulfan Injection and Rifampin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
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.
Questions for your pharmacist
- Does my dose of Busulfan Injection or Rifampin 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 (2)
- Drangines C, Laquet J, & Kunwor R: A clinically relevant drug interaction between busulfan and rifampin in the setting of hematopoietic stem cell transplant conditioning. Pharmacol Res Perspect 2026; 14(2):e70230. DOI
- Domingos V, Nezvalova-Henriksen K, Dadkhah A, et al: A practical guide to therapeutic drug monitoring in busulfan: recommendations from the Pharmacist Committee of the European Society for Blood and Marrow Transplantation (EBMT). Bone Marrow Transplant 2024; 59(12):1641-1653. PubMed
Keep reading about Rifampin
Keep reading about Busulfan Injection
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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