What the FDA labels say about taking them together
Ivacaftor and warfarin
Ivacaftor's FDA label of March 23, 2026 names warfarin in its drug interactions section; the warfarin label PlainMeds reads does not name ivacaftor. The ivacaftor label: “… international normalized ratio (INR) during co-administration of KALYDECO with warfarin is recommended.”
Check it at the source: the ivacaftor FDA label on DailyMed (effective March 23, 2026, Vertex Pharmaceuticals Incorporated); the warfarin FDA label on DailyMed (effective May 29, 2026, Amneal Pharmaceuticals LLC).
What does the ivacaftor label say about warfarin?
Ivacaftor label, drug interactionsPotential for ivacaftor to affect other drugs 7.4 CYP2C9 Substrates Ivacaftor may inhibit CYP2C9; therefore, monitoring of the international normalized ratio (INR) during co-administration of KALYDECO with warfarin is recommended.
Source: FDA drug label (Kalydeco), Vertex Pharmaceuticals Incorporated, effective March 23, 2026 (SPL set 0ab0c9f8-3eee-4e0f-9f3f-c1e16aaffe25), via openFDA; the full label on DailyMed
What does the warfarin label say about ivacaftor?
Warfarin's label (effective May 29, 2026) does not name ivacaftor 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
| Ivacaftor | Warfarin | |
|---|---|---|
| Labeled for | n/a | Blood clots (DVT and PE), Atrial fibrillation |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | n/a | $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