What the FDA labels say about taking them together
Phenytoin and sufentanil
Sufentanil's FDA label of June 1, 2026 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name sufentanil. The sufentanil label: “The concomitant use of Sufentanil Citrate Injection and CYP3A4 inducers can decrease the plasma concentration of sufentanil, resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have …”
Check it at the source: the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.); the sufentanil FDA label on DailyMed (effective June 1, 2026, Hospira, Inc.).
What does the phenytoin label say about sufentanil?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name sufentanil 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 sufentanil label say about phenytoin?
Sufentanil label, drug interactionsCYP3A4 Inducers Clinical Impact: The concomitant use of Sufentanil Citrate Injection and CYP3A4 inducers can decrease the plasma concentration of sufentanil, resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence to sufentanil. … Injection dosage reduction and monitor for signs of respiratory depression. Examples: Rifampin, carbamazepine, phenytoin
Sufentanil label, warnings and precautionsSimilarly, discontinuation of a CYP3A4 inducer, such as rifampin, carbamazepine, and phenytoin, in Sufentanil Citrate Injection-treated patients may increase sufentanil plasma concentrations and prolong opioid adverse reactions.
Source: FDA drug label (Sufentanil Citrate), Hospira, Inc., effective June 1, 2026 (SPL set 20293943-46ff-4345-1aa4-929b4e017a25), 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 | Sufentanil | |
|---|---|---|
| Labeled for | Seizures and epilepsy | n/a |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.145 per capsule 100 mg capsule | n/a |
| Shortage now | No current entry | In shortage |
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