What the FDA labels say about taking them together
Phenytoin and procainamide
Procainamide's FDA label of February 17, 2025 names phenytoin in its warnings section; the phenytoin labels PlainMeds reads (2) do not name procainamide.
Check it at the source: the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.); the procainamide FDA label on DailyMed (effective February 17, 2025, Caplin Steriles Limited).
What does the phenytoin label say about procainamide?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name procainamide 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 procainamide label say about phenytoin?
Procainamide label, warningsTherefore, use of procainamide should be considered only if discontinuation of digitalis, and therapy with potassium, lidocaine, or phenytoin are ineffective.
Source: FDA drug label (Procainamide Hydrochloride), Caplin Steriles Limited, effective February 17, 2025 (SPL set fcaa5e9a-3c8a-4796-aa87-626268b6cf60), 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 | Procainamide | |
|---|---|---|
| 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 | 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