What the FDA labels say about taking them together
Phenytoin and temsirolimus
Temsirolimus's FDA label of December 26, 2025 names phenytoin in its warnings and precautions section; the phenytoin labels PlainMeds reads (2) do not name temsirolimus. The temsirolimus label: “Inducers or Inhibitors of CYP3A Metabolism Agents Inducing CYP3A Metabolism: Strong inducers of CYP3A4/5 such as dexamethasone, carbamazepine, phenytoin, phenobarbital, rifampin, rifabutin, and rifampacin may decrease …”
Check it at the source: the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.); the temsirolimus FDA label on DailyMed (effective December 26, 2025, Wyeth Pharmaceuticals LLC, a subsidiary of Pfizer Inc.).
What does the phenytoin label say about temsirolimus?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name temsirolimus 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 temsirolimus label say about phenytoin?
Temsirolimus label, warnings and precautionsInducers or Inhibitors of CYP3A Metabolism Agents Inducing CYP3A Metabolism: Strong inducers of CYP3A4/5 such as dexamethasone, carbamazepine, phenytoin, phenobarbital, rifampin, rifabutin, and rifampacin may decrease exposure of the active metabolite, sirolimus.
Source: FDA drug label (Torisel), NDA022088 (Pf Prism Cv), as published by Wyeth Pharmaceuticals LLC, a subsidiary of Pfizer Inc., effective December 26, 2025 (SPL set 95b7dc92-2180-42f1-8699-3c28f609e674), 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 | Temsirolimus | |
|---|---|---|
| Labeled for | Seizures and epilepsy | n/a |
| Boxed warning | No | No |
| 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