What the FDA labels say about taking them together
Valproic acid and warfarin
Valproic acid's FDA label of January 24, 2025 names warfarin in its drug interactions section; the warfarin label PlainMeds reads does not name valproic acid. The valproic acid label: “… effective dose Dosage adjustment of amitriptyline/nortriptyline, propofol, warfarin, and zidovudine may be necessary if used concomitantly with Valproic acid Topiramate: Hyperammonemia and encephalopathy”
Check it at the source: the valproic acid FDA label on DailyMed (effective January 24, 2025, PAI Holdings, LLC dba PAI Pharma); the warfarin FDA label on DailyMed (effective May 29, 2026, Amneal Pharmaceuticals LLC).
What does the valproic acid label say about warfarin?
Valproic acid label, drug interactionsMonitoring of valproate concentrations is recommended ( 7.1 ) Co-administration of valproate can affect the pharmacokinetics of other drugs (e.g., diazepam, ethosuximide, lamotrigine, phenytoin) by inhibiting their metabolism or protein binding displacement ( 7.2 ) Patients stabilized on rufinamide should begin valproate therapy at a low dose, and titrate to clinically effective dose ( 7.2 ) Dosage adjustment of amitriptyline/nortriptyline, propofol, warfarin, and zidovudine may be necessary if used concomitantly with Valproic acid ( 7.2 ) Topiramate: Hyperammonemia and encephalopathy
Source: FDA drug label (VALPROIC ACID), PAI Holdings, LLC dba PAI Pharma, effective January 24, 2025 (SPL set 7d5cb52e-37dd-4dfa-a6f4-09f9548846c6), via openFDA; the full label on DailyMed
What does the warfarin label say about valproic acid?
Warfarin's label (effective May 29, 2026) does not name valproic acid in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Warfarin Sodium), Amneal Pharmaceuticals LLC, effective May 29, 2026 (SPL set 558b7a0d-5490-4c1b-802e-3ab3f1efe760), 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
| Valproic acid | Warfarin | |
|---|---|---|
| Labeled for | Seizures and epilepsy, Migraine | Blood clots (DVT and PE), Atrial fibrillation |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.243 per capsule 250 mg capsule | $0.093 per tablet 2 mg tablet |
| Shortage now | Listed; available | 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