Mitomycin and Tamoxifen: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Tamoxifen
Mitomycin
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 risk of hemolytic uremic syndrome
Interaction Deep Dive
One retrospective study has reported a higher risk of hemolytic uremic syndrome associated with the use of tamoxifen in combination with mitomycin compared to chemotherapy alone1.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) A nonrandomized retrospective study comparing 94 patients receiving tamoxifen plus 3M chemotherapy (mitomycin, mitoxantrone, and methotrexate) with 45 patients receiving 3M alone suggests a higher risk of hemolytic uremic syndrome associated with the tamoxifen combination 1. Nine cases (10%) in the tamoxifen group experienced progressive anemia, thrombocytopenia, and renal dysfunction, compared to none in the 3M-only group. One patient died with evidence of HUS on autopsy, 3 patients lived but had persistent HUS, and 3 patients lived with persistent renal dysfunction, while the remaining 2 patients fully recovered. The authors cited the rare occurrence of this syndrome associated with the use of high dose mitomycin (much higher doses than used in this study) as suggestive that this agent rather than the other two is involved in a possible interaction. It should be noted that the 9 patients with the triad of HUS symptoms were significantly older than the mean age of the 3M-only group (63 years vs 47 years). More information is needed regarding this possible drug interaction.
Common questions
Can I take Mitomycin and Tamoxifen together?
Increased risk of hemolytic uremic syndrome Always confirm with your pharmacist or prescriber before making any change.
How serious is the Mitomycin and Tamoxifen 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 "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 Mitomycin or Tamoxifen 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)
- Montes A, Powles TJ, O'Brien MER, et al: A toxic interaction between mitomycin C and tamoxifen causing the haemolytic uraemic syndrome. Eur J Cancer 1993; 29A:1854-1857. DOI
Keep reading about Tamoxifen
Keep reading about Mitomycin
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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