What the FDA labels say about taking them together
Disopyramide and phenytoin
Disopyramide's FDA label of August 24, 2026 names phenytoin in its drug interactions section, and phenytoin's label names disopyramide too. The disopyramide label: “Drug Interactions If phenytoin or other hepatic enzyme inducers are taken concurrently with Norpace or Norpace CR, lower plasma levels of disopyramide may occur.”
Check it at the source: the disopyramide FDA label on DailyMed (effective August 24, 2026, Pfizer Laboratories Div Pfizer Inc); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the disopyramide label say about phenytoin?
Disopyramide label, drug interactionsDrug Interactions If phenytoin or other hepatic enzyme inducers are taken concurrently with Norpace or Norpace CR, lower plasma levels of disopyramide may occur.
Source: FDA drug label (Norpace), Pfizer Laboratories Div Pfizer Inc, effective August 24, 2026 (SPL set e2aa1642-d262-4520-bc6a-9fd3ad795677), via openFDA; the full label on DailyMed
What does the phenytoin label say about disopyramide?
Phenytoin label, drug interactionsInteracting Agent: Other; Examples: Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine
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
| Disopyramide | Phenytoin | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.801 per capsule 100 mg capsule | $0.145 per capsule 100 mg capsule |
| Shortage now | A presentation being discontinued | 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