What the FDA labels say about taking them together
Fosphenytoin and tinidazole
Tinidazole's FDA label of December 27, 2021 names fosphenytoin in its drug interactions section; the fosphenytoin label PlainMeds reads does not name tinidazole. The tinidazole label: “Monitor for toxicities of these immunosuppressive drugs Fluorouracil: Monitor for fluorouracil-associated toxicities Phenytoin, fosphenytoin:”
Check it at the source: the fosphenytoin FDA label on DailyMed (effective May 18, 2025, Pfizer Laboratories Div Pfizer Inc); the tinidazole FDA label on DailyMed (effective December 27, 2021, Mission Pharmacal Company).
What does the fosphenytoin label say about tinidazole?
Fosphenytoin's label (effective May 18, 2025) does not name tinidazole in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (CEREBYX), NDA020450 (Parke Davis), as published by Pfizer Laboratories Div Pfizer Inc, effective May 18, 2025 (SPL set de5a6711-4abb-4c3d-a18b-266b094ace11), via openFDA; the full label on DailyMed
What does the tinidazole label say about fosphenytoin?
Tinidazole label, drug interactionsMonitor for toxicities of these immunosuppressive drugs ( 7.1 ) Fluorouracil: Monitor for fluorouracil-associated toxicities ( 7.1 ) Phenytoin, fosphenytoin:
Source: FDA drug label (Tindamax), Mission Pharmacal Company, effective December 27, 2021 (SPL set a0d01539-8413-4703-94cc-d221918630a1), 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
| Fosphenytoin | Tinidazole | |
|---|---|---|
| Labeled for | Seizures and epilepsy | n/a |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | n/a | $2.35 per tablet 500 mg tablet |
| Shortage now | No current entry | No current entry |
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