Ifosfamide Injection and Primidone: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Primidone
Ifosfamide 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 neurotoxic and nephrotoxic effects, reduced ifosfamide exposure and reduced efficacy of ifosfamide
Interaction Deep Dive
Ifosfamide is a substrate for CYP3A4 and PHENobarbital is a CYP3A4 inducer. Concomitant administration of ifosfamide and CYP3A4 inducers may increase the metabolism of ifosfamide to its active alkylating metabolites and may increase the formation of a neurotoxic and nephrotoxic metabolite. Patients taking ifosfamide and CYP3A4 inducers, such as PHENobarbital, should be carefully monitored for toxicity, and ifosfamide dose adjustment may be required1. Also, concomitant use of PHENobarbital (a CYP2B6/CYP3A inducer) with ifosfamide (a CYP2B6/CYP3A substrate) may decrease ifosfamide exposure, which may reduce the efficacy of ifosfamide. If concomitant use cannot be avoided, closely monitor neonates and consider increasing the ifosfamide dosage accordingly 2.
Why it happens (mechanism)
Induction of CYP3A4-mediated metabolism of ifosfamide to a neurotoxic and nephrotoxic metabolite; induction of CYP2B6-mediated metabolism of ifosfamide
Common questions
Can I take Ifosfamide Injection and Primidone together?
Increased neurotoxic and nephrotoxic effects, reduced ifosfamide exposure and reduced efficacy of ifosfamide Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ifosfamide Injection and Primidone 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Ifosfamide Injection or Primidone 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)
- Product Information: IFEX(TM) intravenous injection, ifosfamide intravenous injection. Baxter Healthcare Corporation (per FDA), Deerfield, IL, 2012. DailyMed
- Product Information: SEZABY(TM) intravenous injection, phenobarbital sodium intravenous injection. Sun Pharmaceutical Industries Inc (per manufacturer), Cranbury, NJ, 2022. DailyMed
Keep reading about Primidone
Keep reading about Ifosfamide 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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist