What the FDA labels say about taking them together
Cyclophosphamide and metronidazole
Cyclophosphamide's FDA label of January 19, 2026 names metronidazole in its drug interactions section; the metronidazole labels PlainMeds reads (4) do not name cyclophosphamide. The cyclophosphamide label: “Monitor for neurologic toxicities in patients receiving metronidazole.”
Check it at the source: the cyclophosphamide FDA label on DailyMed (effective January 19, 2026, Amneal Pharmaceuticals LLC); the metronidazole FDA label on DailyMed (effective September 3, 2024, Aurobindo Pharma Limited).
What does the cyclophosphamide label say about metronidazole?
Cyclophosphamide label, drug interactionsMonitor for neurologic toxicities in patients receiving metronidazole.
Cyclophosphamide label (Eugia US LLC, April 21, 2025), drug interactionsIn an animal study, the combination of cyclophosphamide with metronidazole was associated with increased cyclophosphamide toxicity.
Source: FDA drug label (Cyclophosphamide, NDA210735), Eugia US LLC, effective April 21, 2025 (SPL set 3c1eb470-0bba-457d-94e3-b9508f0d398a), via openFDA
Source: FDA drug label (Cyclophosphamide), Amneal Pharmaceuticals LLC, effective January 19, 2026 (SPL set 520bfe39-dfd5-4a20-9a37-80078afded0d), via openFDA; the full label on DailyMed
What does the metronidazole label say about cyclophosphamide?
Metronidazole's label (effective September 3, 2024) and its 3 other brand-application labels do not name cyclophosphamide in these sections. A label lists what its studies and reports found; it is not a complete list.
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
| Cyclophosphamide | Metronidazole | |
|---|---|---|
| Labeled for | Leukemia, lymphoma and myeloma | Bacterial infections |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.67 per capsule 50 mg capsule | $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