Doxifluridine and Methotrexate Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Methotrexate Injection
Doxifluridine
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
Increased 5-fluorouracil toxicity
Interaction Deep Dive
Concomitant use of methotrexate with tegafur, which is converted to 5-fluorouracil after absorption, or tegafur-containing products may increase 5-fluorouracil toxicity and should be approached with caution1. If coadministration is necessary, monitor for 5-fluorouracil toxicity and consider dose adjustments if necessary.
Why it happens (mechanism)
Inhibition of thymidylate synthase and dihydrofolate reductase by methotrexate
Common questions
Can I take Doxifluridine and Methotrexate Injection together?
Increased 5-fluorouracil toxicity Always confirm with your pharmacist or prescriber before making any change.
How serious is the Doxifluridine and Methotrexate Injection 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.
Questions for your pharmacist
- Does my dose of Doxifluridine or Methotrexate Injection 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 (1)
- Product Information: Teysuno oral capsules, tegafur gimeracil oteracil oral capsules. Nordic Group BV (per EMA), Hoofddorp, The Netherlands, 2012.
Keep reading about Methotrexate Injection
Keep reading about Doxifluridine
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