Capecitabine and Secnidazole: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Secnidazole
Capecitabine
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 exposure of 5-fluorouracil
Interaction Deep Dive
Use caution with concomitant use of 5-fluorouracil prodrugs (capecitabine, doxifluridine, fluorouracil, tegafur) with nitroimidazoles, including metronidazole and misonidazole. Nitroimidazoles may decrease the clearance of 5-fluorouracil, thereby increasing 5-fluorouracil exposure1. Co-administered metronidazole significantly reduced fluorouracil clearance resulting in more severe fluorouracil side effects, without enhanced therapeutic results 3. If coadministration is required of a nitroimidazole with fluorouracil or one of its inactive prodrugs, monitor for fluorouracil toxicity (granulocytopenia, anemia, thrombocytopenia, stomatitis, vomiting) 2 .
Why it happens (mechanism)
Decreased clearance of 5-fluorouracil
Literature reports
1 report — tap to read
a) A total of 27 patients with metastatic colorectal cancer received daily metronidazole 750 mg/m(2) followed in an hour by fluorouracil 600 mg/m(2), both drugs given intravenously, for five consecutive days. This treatment was repeated every four weeks until prohibitive toxicity or disease progression occurred. The pharmacokinetics of fluorouracil, measured in 10 patients, showed a reduction in fluorouracil clearance of 26.9%, and increases of 34% and 38%, respectively, in the area under the concentration-time curve (AUC) and half-life of fluorouracil during combined therapy. The incidence of toxic effects of the metronidazole-fluorouracil regimen included granulocytopenia (74%), anemia (41%), thrombocytopenia (19%), severe stomatitis and oral ulceration (34%), intractable nausea and vomiting (22%), and peripheral neuropathy with paresthesia and weakness (7%). In vitro, metronidazole combined with fluorouracil did not enhance antitumor activity over 5-FU alone 3.
Common questions
Can I take Capecitabine and Secnidazole together?
Increased exposure of 5-fluorouracil Always confirm with your pharmacist or prescriber before making any change.
How serious is the Capecitabine and Secnidazole 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 Capecitabine or Secnidazole 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: Teysuno oral capsules, tegafur gimeracil oteracil oral capsules. Nordic Group BV (per EMA), Hoofddorp, The Netherlands, 2012.
- Product Information: TINDAMAX(R) oral tablets, tinidazole oral tablets. Mission Pharmacal Company, San Antonio, TX, 2007. DailyMed
- Bardakji Z, Jolivet J, Langelier Y, et al: 5-Fluorouracil-metronidazole combination therapy in metastatic colorectal cancer. Cancer Chemother Pharmacol 1986; 18:140-144. DOI
Keep reading about Secnidazole
Keep reading about Capecitabine
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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