What the FDA labels say about taking them together
Tamoxifen and warfarin
Tamoxifen's FDA label (Soltamox) of November 29, 2021 names warfarin in its contraindications section; the warfarin label PlainMeds reads does not name tamoxifen. The tamoxifen label: “Warfarin A marked increase in anticoagulant effect may occur when tamoxifen is used in combination with warfarin.”
Check it at the source: the tamoxifen FDA label on DailyMed (effective December 18, 2025, Actavis Pharma, Inc.); the warfarin FDA label on DailyMed (effective May 29, 2026, Amneal Pharmaceuticals LLC).
What does the tamoxifen label say about warfarin?
Soltamox label (Mayne Pharma, November 29, 2021), contraindicationsSOLTAMOX is contraindicated in patients who require concomitant warfarin therapy or have a history of deep vein thrombosis or pulmonary embolus if the indication for treatment is either reduction of breast cancer incidence in high-risk patients or risk reduction of invasive breast cancer after treatment of DCIS [see Warnings and Precautions (5.2) and Drug Interactions (7.2) ].
Soltamox label (Mayne Pharma, November 29, 2021), drug interactionsWarfarin A marked increase in anticoagulant effect may occur when tamoxifen is used in combination with warfarin.
Source: FDA drug label (Soltamox, NDA021807), Mayne Pharma, effective November 29, 2021 (SPL set 1e6ff055-590c-41e6-9530-1fdf04cdbd02), via openFDA
Source: FDA drug label (Tamoxifen Citrate), Actavis Pharma, Inc., effective December 18, 2025 (SPL set 9b8a4211-120f-4981-ad69-928accb97637), via openFDA; the full label on DailyMed
What does the warfarin label say about tamoxifen?
Warfarin's label (effective May 29, 2026) does not name tamoxifen 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
| Tamoxifen | Warfarin | |
|---|---|---|
| Labeled for | Breast cancer | Blood clots (DVT and PE), Atrial fibrillation |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.277 per tablet 20 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