Busulfan Injection and Itraconazole: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Itraconazole
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
Increased busulfan exposure and an increased risk of busulfan-related adverse effects
Interaction Deep Dive
Concomitant administration of itraconazole with busulfan increases the busulfan exposure due to decreased busulfan clearance by itraconazole. Itraconazole decreased busulfan clearance by up to 25%, increasing the risk of side effects1. Monitor for busulfan-related adverse reactions when administered concomitantly. Busulfan dose reduction may be necessary 2.
Why it happens (mechanism)
Reduced busulfan clearance
Literature reports
1 report — tap to read
a) In a study involving 52 patients (31 males, 21 females; mean age 25 years old) during a busulfan (4 mg/kg/day for four days) conditioning regimen for bone marrow transplantation, three treatments groups were formed. Thirteen patients were treated with oral itraconazole (6 mg/kg/day), 13 were treated with oral fluconazole (6 mg/kg/day) and 26 patients did not receive any antifungal treatment. The mean busulfan clearance in the control group was 9.373 L/h/square meter, 10.103 L/h/square meter in the fluconazole group, and 7.653 L/h/square meter in the itraconazole group (p less than 0.01 versus control and versus fluconazole). The average busulfan plasma concentration at steady-state for the control, fluconazole, and itraconazole groups was 639.97 ng/mL, 609.73 ng/mL (p=NS versus control), 798.38 ng/mL (p less than 0.01 versus control and versus fluconazole), respectively. Sixty-nine percent of patients receiving itraconazole experienced grade II-III regimen-related toxicity, while only 23% in the fluconazole group and 38% in the control group experienced toxicity 3.
Common questions
Can I take Busulfan Injection and Itraconazole together?
Increased busulfan exposure and an increased risk of busulfan-related adverse effects Always confirm with your pharmacist or prescriber before making any change.
How serious is the Busulfan Injection and Itraconazole 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 "established". Well documented — supported by controlled studies or strong clinical data.
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 Itraconazole 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: BUSULFEX(R) intravenous injection, busulfan intravenous injection. Otsuka America Pharmaceutical Inc (per FDA), Rockville, MD, 2018. DailyMed
- Product Information: SPORANOX(R) oral capsules, itraconazole oral capsules. Janssen Pharmaceuticals Inc (per FDA), Titusville, NJ, 2022. DailyMed
- Buggia I, Zecca M, Alessandrino EP, et al: Itraconazole can increase systemic exposure to busulfan in patients given bone marrow transplantation. Anticancer Res 1996; 16:2083-2088.
Keep reading about Itraconazole
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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