What the FDA labels say about taking them together
Phenytoin and vincristine
Vincristine's FDA label of February 17, 2026 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name vincristine. The vincristine label: “Drug Interactions The simultaneous oral or intravenous administration of phenytoin and antineoplastic chemotherapy combinations that included vincristine sulfate has been reported to reduce blood levels of the …”
Check it at the source: the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.); the vincristine FDA label on DailyMed (effective February 17, 2026, Hospira, Inc.).
What does the phenytoin label say about vincristine?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name vincristine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Phenytek), Mylan Pharmaceuticals Inc., effective October 15, 2024 (SPL set 0f94c791-8b07-4b41-927e-c9f28bec5f60), via openFDA; the full label on DailyMed
What does the vincristine label say about phenytoin?
Vincristine label, drug interactionsDrug Interactions The simultaneous oral or intravenous administration of phenytoin and antineoplastic chemotherapy combinations that included vincristine sulfate has been reported to reduce blood levels of the anticonvulsant and to increase seizure activity.
Source: FDA drug label (VinCRIStine Sulfate), Hospira, Inc., effective February 17, 2026 (SPL set b22e4c8e-dbe1-4d4b-a026-e1812974071c), 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
| Phenytoin | Vincristine | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Leukemia, lymphoma and myeloma |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.145 per capsule 100 mg capsule | n/a |
| 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