What the FDA labels say about taking them together
Phenytoin and toremifene
Toremifene's FDA label of November 13, 2024 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name toremifene. The toremifene label: “… avoided. CYP2C9 substrates with a narrow therapeutic index such as warfarin or phenytoin with FARESTON should be used with caution and require careful monitoring.”
Check it at the source: the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.); the toremifene FDA label on DailyMed (effective November 13, 2024, Kyowa Kirin, Inc.).
What does the phenytoin label say about toremifene?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name toremifene 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 toremifene label say about phenytoin?
Toremifene label, drug interactionsDRUG INTERACTIONS Drugs that decrease renal calcium excretion, e.g., thiazide diuretics, may increase the risk of hypercalcemia in patients receiving FARESTON. ( 7.1 ) Agents that prolong QT should be avoided. ( 7.2 ) Coadministration with a strong CYP3A4 inducer may result in a relevant decrease in FARESTON exposure and should be avoided. ( 7.3 ) Coadministration with a strong CYP3A4 inhibitor can result in a relevant increase in FARESTON exposure and should be avoided. ( 7.4 ) CYP2C9 substrates with a narrow therapeutic index such as warfarin or phenytoin with FARESTON should be used with caution and require careful monitoring.
Source: FDA drug label (Fareston), Kyowa Kirin, Inc., effective November 13, 2024 (SPL set 2cab8dd1-3a10-48e6-86ce-0e5275ed49e5), 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 | Toremifene | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Breast cancer |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.145 per capsule 100 mg capsule | $19.60 per tablet 60 mg tablet |
| 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