What the FDA labels say about taking them together
Palbociclib and phenytoin
Palbociclib's FDA label of July 2, 2026 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name palbociclib. The palbociclib label: “Avoid concomitant use of strong CYP3A inducers.”
Check it at the source: the palbociclib FDA label on DailyMed (effective July 2, 2026, Pfizer Laboratories Div Pfizer Inc); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the palbociclib label say about phenytoin?
Palbociclib label, drug interactionsAvoid concomitant use of strong CYP3A inducers (e.g., phenytoin, rifampin, carbamazepine, enzalutamide, and St John's Wort) [see Clinical Pharmacology (12.3) ].
Source: FDA drug label (Ibrance), Pfizer Laboratories Div Pfizer Inc, effective July 2, 2026 (SPL set fecbdd7d-b729-41b5-9872-231b8fe104ce), via openFDA; the full label on DailyMed
What does the phenytoin label say about palbociclib?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name palbociclib 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
| Palbociclib | Phenytoin | |
|---|---|---|
| Labeled for | Breast cancer | Seizures and epilepsy |
| Boxed warning | No | 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