What the FDA labels say about taking them together
Cobimetinib and phenytoin
Cobimetinib's FDA label of July 29, 2026 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name cobimetinib. The cobimetinib label: “Avoid concurrent use of COTELLIC and strong or moderate CYP3A inducers including but not limited to carbamazepine, efavirenz, phenytoin, rifampin, and St. John's Wort.”
Check it at the source: the cobimetinib FDA label on DailyMed (effective July 29, 2026, Genentech, Inc.); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the cobimetinib label say about phenytoin?
Cobimetinib label, drug interactionsAvoid concurrent use of COTELLIC and strong or moderate CYP3A inducers including but not limited to carbamazepine, efavirenz, phenytoin, rifampin, and St. John's Wort [see Clinical Pharmacology (12.3) ].
Source: FDA drug label (Cotellic), Genentech, Inc., effective July 29, 2026 (SPL set c387579e-cee0-4334-bd1e-73f93ac1bde6), via openFDA; the full label on DailyMed
What does the phenytoin label say about cobimetinib?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name cobimetinib 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
| Cobimetinib | Phenytoin | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.145 per capsule 100 mg capsule |
| 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