Two medicines, side by side
Anastrozole vs tamoxifen
Anastrozole and tamoxifen are both labeled for breast cancer. Drugs@FDA records approvals of anastrozole since 1995 and of tamoxifen since 1977. Pharmacies paid $0.142 per anastrozole 1 mg tablet and $0.277 per tamoxifen 20 mg tablet (NADAC, October 7, 2026); the strengths differ, so the two prices are not like for like. In FDA's classes, anastrozole is an aromatase inhibitor and tamoxifen an estrogen agonist/antagonist.
Check it at the source: the anastrozole FDA label on DailyMed (effective March 2, 2026); the tamoxifen FDA label on DailyMed (effective December 18, 2025).
Highlights of the anastrozole record
Anastrozole (Arimidex) · label of March 2, 2026
Used for
From the label: indicationsARIMIDEX is an aromatase inhibitor indicated for: • Adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer ( 1.1 ) • First-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor-unknown locally advanced or metastatic breast cancer ( 1.2 ) • Treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy. […]
On the market
- Earliest approval on file
- December 27, 1995
- Generic labelers
- 24 labelers
- Pharmacy cost
- $0.142 per tablet
Supply and safety
- Shortage
- No current entry
- Recalls
- 4
Highlights of the tamoxifen record
Tamoxifen (Nolvadex) · label of December 18, 2025
For Women with Ductal Carcinoma in Situ (DCIS) and Women at High Risk for Breast Cancer Serious and life-threatening events associated with tamoxifen in the risk reduction setting (women at high risk for cancer and women with DCIS) include uterine malignancies, stroke and pulmonary embolism. Incidence rates for these events were estimated from the NSABP P-1 trial (see CLINICAL PHARMACOLOGY, Clinical Studies, Reduction in Breast Cancer Incidence in High Risk Women ).
Used for
From the label: indicationsMetastatic Breast Cancer: Tamoxifen citrate tablets, USP are effective in the treatment of metastatic breast cancer in women and men. In premenopausal women with metastatic breast cancer, tamoxifen is an alternative to oophorectomy or ovarian irradiation. Available evidence indicates that patients whose tumors are estrogen receptor positive are more likely to benefit from tamoxifen therapy. […]
On the market
- Earliest approval on file
- December 30, 1977
- Generic labelers
- 10 labelers
- Pharmacy cost
- $0.277 per tablet
Supply and safety
- Shortage
- No current entry
- Recalls
- 0
Source: FDA drug labels via openFDA (Anastrozole label of March 2, 2026, Tamoxifen label of December 18, 2025); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do anastrozole and tamoxifen differ on the record?
In FDA's classes, anastrozole is an aromatase inhibitor and tamoxifen an estrogen agonist/antagonist.
Half-life, in each label's words: Anastrozole, “The mean elimination half-life of anastrozole is 50 hours.”; Tamoxifen, “The decline in plasma concentrations of tamoxifen is biphasic with a terminal elimination half-life of about 5 to 7 …”
Only the tamoxifen label carries a boxed warning.
Generics: anastrozole since 2010; tamoxifen since 2003 (Drugs@FDA).
| Anastrozole | Tamoxifen | |
|---|---|---|
| Labeled for | Breast cancer | Breast cancer |
| Pharmacologic class | Aromatase Inhibitor | Estrogen Agonist/Antagonist |
| How it works (label) | The growth of many cancers of the breast is stimulated or maintained by estrogens. | n/a |
| Half-life (label) | The mean elimination half-life of anastrozole is 50 hours. | The decline in plasma concentrations of tamoxifen is biphasic with a terminal elimination half-life of about 5 to 7 days. |
| Earliest approval on file (Drugs@FDA) | December 27, 1995 | December 30, 1977 |
| First generic approved | June 28, 2010 | February 20, 2003 |
| Generic labelers (NDC) | 24 labelers | 10 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.142 per tablet (Anastrozole 1 mg tablet) | $0.277 per tablet (Tamoxifen 20 mg tablet) |
| 12-month price change | +3% | -2% |
| Boxed warning | No | Yes |
| Shortage now | No current entry | No current entry |
| Recalls recorded | 4 | 0 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 36,521 | 5,727 |
| DEA schedule | none | none |
Source: Drugs@FDA, FDA NDC Directory, CMS NADAC of October 7, 2026, FDA shortages and recalls, FAERS via openFDA (FDA files October 8, 2026)
Do their labels mention each other?
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.
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 ).
Tamoxifen label, drug interactionsDRUG INTERACTIONS Anastrozole and letrozole: Should not be used in combination with tamoxifen.
Source: FDA drug labels via openFDA
What next?
- Alternatives to anastrozole
- every medicine labeled for the same conditions