What the FDA labels say about taking them together
Methimazole and warfarin
Methimazole's FDA label of August 20, 2026 names warfarin in its drug interactions section; the warfarin label PlainMeds reads does not name methimazole. The methimazole label: “Drug Interactions Anticoagulants (oral): Due to potential inhibition of vitamin K activity by methimazole, the activity of oral anticoagulants (e.g., warfarin) may be increased; …”
Check it at the source: the methimazole FDA label on DailyMed (effective August 20, 2026, AiPing Pharmaceutical, Inc.); the warfarin FDA label on DailyMed (effective May 29, 2026, Amneal Pharmaceuticals LLC).
What does the methimazole label say about warfarin?
Methimazole label, drug interactionsDrug Interactions Anticoagulants (oral): Due to potential inhibition of vitamin K activity by methimazole, the activity of oral anticoagulants (e.g., warfarin) may be increased; additional monitoring of PT/INR should be considered, especially before surgical procedures. ß-adrenergic blocking agents:
Source: FDA drug label (Methimazole), AiPing Pharmaceutical, Inc., effective August 20, 2026 (SPL set 06bb4bcc-5e47-48b6-a76c-648f846704e8), via openFDA; the full label on DailyMed
What does the warfarin label say about methimazole?
Warfarin's label (effective May 29, 2026) does not name methimazole 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
| Methimazole | Warfarin | |
|---|---|---|
| Labeled for | n/a | Blood clots (DVT and PE), Atrial fibrillation |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.0702 per tablet 5 mg tablet | $0.093 per tablet 2 mg tablet |
| 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