What the FDA labels say about taking them together
Fluorouracil and metronidazole
Metronidazole's FDA label (Metronidazole) of June 12, 2025 names fluorouracil in its drug interactions section; the fluorouracil labels PlainMeds reads (4) do not name metronidazole. The metronidazole label: “Fluorouracil Metronidazole Injection decreases the clearance of 5-fluorouracil and may therefore cause 5-fluorouracil toxicity.”
Check it at the source: the fluorouracil FDA label on DailyMed (effective January 19, 2026, Eugia US LLC); the metronidazole FDA label on DailyMed (effective September 3, 2024, Aurobindo Pharma Limited).
What does the fluorouracil label say about metronidazole?
Fluorouracil's label (effective January 19, 2026) and its 3 other brand-application labels do not name metronidazole in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (FLUOROURACIL), Eugia US LLC, effective January 19, 2026 (SPL set 697816ce-dc05-4943-b7f0-2f0b125e93b7), via openFDA; the full label on DailyMed
What does the metronidazole label say about fluorouracil?
Metronidazole label (Baxter Healthcare Corporation, June 12, 2025), drug interactionsFluorouracil Metronidazole Injection decreases the clearance of 5-fluorouracil and may therefore cause 5-fluorouracil toxicity.
Source: FDA drug label (Metronidazole, NDA018657), Baxter Healthcare Corporation, effective June 12, 2025 (SPL set d2112f37-5080-4a19-bcc3-6386b49abe1d), via openFDA
Source: FDA drug label (Metronidazole), Aurobindo Pharma Limited, effective September 3, 2024 (SPL set f68397ee-67db-472e-8607-4300064e37df), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Fluorouracil | Metronidazole | |
|---|---|---|
| Labeled for | Colorectal cancer | Bacterial infections |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.616 per gram 5% cream | $0.102 per tablet 250 mg tablet |
| Shortage now | No current entry | In shortage |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once