What the FDA labels say about taking them together
Anastrozole and tamoxifen
Anastrozole's FDA label of March 2, 2026 names tamoxifen in its drug interactions section, and tamoxifen's label names anastrozole too. The anastrozole label: “Tamoxifen Co-administration of anastrozole and tamoxifen in breast cancer patients reduced anastrozole plasma concentration by 27%.”
Check it at the source: the anastrozole FDA label on DailyMed (effective March 2, 2026, ANI Pharmaceuticals, Inc.); the tamoxifen FDA label on DailyMed (effective December 18, 2025, Actavis Pharma, Inc.).
What does the anastrozole label say about tamoxifen?
Anastrozole label, drug interactionsTamoxifen Co-administration of anastrozole and tamoxifen in breast cancer patients reduced anastrozole plasma concentration by 27%.
Anastrozole label, warnings and precautionsIn women with pre-existing ischemic heart disease, an increased incidence of ischemic cardiovascular events occurred with ARIMIDEX use compared to tamoxifen use. Consider risks and benefits.
Source: FDA drug label (ARIMIDEX), NDA020541 (Ani Pharms), as published by ANI Pharmaceuticals, Inc., effective March 2, 2026 (SPL set acbfaaa9-503c-4691-9828-76a7146ed6de), via openFDA; the full label on DailyMed
What does the tamoxifen label say about anastrozole?
Tamoxifen label, drug interactionsBased on clinical and pharmacokinetic results from the anastrozole adjuvant trial, tamoxifen citrate should not be administered with anastrozole (see CLINICAL PHARMACOLOGY, Drug-Drug Interactions ).
Soltamox label (Mayne Pharma, November 29, 2021), drug interactionsDRUG INTERACTIONS Anastrozole and letrozole: Should not be used in combination with tamoxifen.
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
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
| Anastrozole | Tamoxifen | |
|---|---|---|
| Labeled for | Breast cancer | Breast cancer |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.142 per tablet 1 mg tablet | $0.277 per tablet 20 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