What the FDA labels say about taking them together
Phenytoin and vinblastine
Vinblastine's FDA label of April 15, 2025 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name vinblastine. The vinblastine label: “Drug Interactions The simultaneous oral or intravenous administration of phenytoin and antineoplastic chemotherapy combinations that included vinblastine sulfate has been reported to have reduced blood levels of the …”
Check it at the source: the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.); the vinblastine FDA label on DailyMed (effective April 15, 2025, Fresenius Kabi USA, LLC).
What does the phenytoin label say about vinblastine?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name vinblastine 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 vinblastine label say about phenytoin?
Vinblastine label, drug interactionsDrug Interactions The simultaneous oral or intravenous administration of phenytoin and antineoplastic chemotherapy combinations that included vinblastine sulfate has been reported to have reduced blood levels of the anticonvulsant and to have increased seizure activity.
Source: FDA drug label (Vinblastine Sulfate), Fresenius Kabi USA, LLC, effective April 15, 2025 (SPL set f073b58e-56d6-4c8d-a2ce-b37719402d77), 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 | Vinblastine | |
|---|---|---|
| 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