What the FDA labels say about taking them together
Busulfan and phenytoin
Busulfan's FDA label of June 27, 2024 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name busulfan. The busulfan label: “Drugs that Increase Busulfan Clearance Phenytoin increases the clearance of busulfan by 15% or more, possibly due to the induction of glutathione-S-transferase.”
Check it at the source: the busulfan FDA label on DailyMed (effective June 27, 2024, Eugia US LLC); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the busulfan label say about phenytoin?
Busulfan label, drug interactionsDrugs that Increase Busulfan Clearance Phenytoin increases the clearance of busulfan by 15% or more, possibly due to the induction of glutathione-S-transferase.
Busulfan label, warnings and precautionsDespite prophylactic therapy with phenytoin, one seizure (1/42 patients) was reported during an autologous transplantation clinical trial of busulfan.
Source: FDA drug label (Busulfan), Eugia US LLC, effective June 27, 2024 (SPL set 06883ac0-4b2a-4f26-89bf-512d37b9ba7f), via openFDA; the full label on DailyMed
What does the phenytoin label say about busulfan?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name busulfan 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
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
| Busulfan | Phenytoin | |
|---|---|---|
| Labeled for | Leukemia, lymphoma and myeloma | Seizures and epilepsy |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | n/a | $0.145 per capsule 100 mg capsule |
| Shortage now | A presentation being discontinued | 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