What the FDA labels say about taking them together
Erythromycin and phenytoin
Erythromycin's FDA label of August 1, 2024 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name erythromycin. The erythromycin label: “… with drugs not thought to be metabolized by CYP3A, including hexobarbital, phenytoin, and valproate.”
Check it at the source: the erythromycin FDA label on DailyMed (effective August 1, 2024, Teva Pharmaceuticals USA, Inc.); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the erythromycin label say about phenytoin?
Erythromycin label, drug interactionsIn addition, there have been reports of interactions of erythromycin with drugs not thought to be metabolized by CYP3A, including hexobarbital, phenytoin, and valproate.
Ery-Ped label (Azurity Pharmaceuticals, Inc. (formerly Arbor Pharmaceuticals), December 16, 2023), drug interactionsConcomitant administration of erythromycin with cisapride, pimozide, astemizole, or terfenadine is contraindicated. (See CONTRAINDICATIONS .) In addition, there have been reports of interactions of erythromycin with drugs not thought to be metabolized by CYP3A, including hexobarbital, phenytoin, and valproate.
Source: FDA drug label (Ery-Ped, NDA050207), Azurity Pharmaceuticals, Inc. (formerly Arbor Pharmaceuticals), effective December 16, 2023 (SPL set 04775721-ab87-4b66-808c-d67a21032385), via openFDA
Source: FDA drug label (Erythromycin), Teva Pharmaceuticals USA, Inc., effective August 1, 2024 (SPL set 75a0bd5a-d09f-483b-bfd8-f8343b149eb2), via openFDA; the full label on DailyMed
What does the phenytoin label say about erythromycin?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name erythromycin 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
| Erythromycin | Phenytoin | |
|---|---|---|
| Labeled for | Bacterial infections, Acne | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $1.96 per tablet 250 mg tablet | $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