Two medicines, side by side
Exemestane vs tamoxifen
Exemestane and tamoxifen are both labeled for breast cancer. Drugs@FDA records approvals of exemestane since 1999 and of tamoxifen since 1977. Pharmacies paid $0.748 per exemestane 25 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, exemestane is an aromatase inhibitor and tamoxifen an estrogen agonist/antagonist.
Check it at the source: the exemestane FDA label on DailyMed (effective September 12, 2024); the tamoxifen FDA label on DailyMed (effective December 18, 2025).
Highlights of the exemestane record
Exemestane (Aromasin) · label of September 12, 2024
Used for
From the label: indicationsExemestane tablets are an aromatase inhibitor indicated for: adjuvant treatment of postmenopausal women with estrogen-receptor positive early breast cancer who have received two to three years of tamoxifen and are switched to exemestane tablets for completion of a total of five consecutive years of adjuvant hormonal therapy ( 14.1 ). treatment of advanced breast cancer in postmenopausal women whose disease has […]
On the market
- Earliest approval on file
- October 21, 1999
- Generic labelers
- 10 labelers
- Pharmacy cost
- $0.748 per tablet
Supply and safety
- Shortage
- No current entry
- Recalls
- 0
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 (Exemestane label of September 12, 2024, Tamoxifen label of December 18, 2025); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do exemestane and tamoxifen differ on the record?
In FDA's classes, exemestane is an aromatase inhibitor and tamoxifen an estrogen agonist/antagonist.
Half-life, in each label's words: Exemestane, “12.3 Pharmacokinetics Following oral administration to healthy postmenopausal women, plasma concentrations of …”; 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: exemestane since 2011; tamoxifen since 2003 (Drugs@FDA).
| Exemestane | Tamoxifen | |
|---|---|---|
| Labeled for | Breast cancer | Breast cancer |
| Pharmacologic class | Aromatase Inhibitor | Estrogen Agonist/Antagonist |
| How it works (label) | Breast cancer cell growth may be estrogen-dependent. Aromatase is the principal enzyme that converts androgens to estrogens both in pre- and postmenopausal women. | n/a |
| Half-life (label) | 12.3 Pharmacokinetics Following oral administration to healthy postmenopausal women, plasma concentrations of exemestane decline polyexponentially with a mean terminal half-life of about 24 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) | October 21, 1999 | December 30, 1977 |
| First generic approved | April 1, 2011 | February 20, 2003 |
| Generic labelers (NDC) | 10 labelers | 10 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.748 per tablet (Exemestane 25 mg tablet) | $0.277 per tablet (Tamoxifen 20 mg tablet) |
| 12-month price change | +7% | -2% |
| Boxed warning | No | Yes |
| Shortage now | No current entry | No current entry |
| Recalls recorded | 0 | 0 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 21,298 | 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?
Exemestane label, warnings and precautionsPercent Change in BMD from Baseline to 24 months, Exemestane vs. Control 1 IES 027 BMD Exemestane N=29 Tamoxifen 1 N=38 Exemestane N=59 Placebo 1 N=65 Lumbar spine (%) -3.1 -0.2 -3.5 -2.4 Femoral neck (%) -4.2 -0.3 -4.6 -2.6 During adjuvant treatment with exemestane, women with osteoporosis or at risk of osteoporosis should have their bone mineral density formally assessed by bone densitometry at the commencement of …
Source: FDA drug labels via openFDA
What next?
- Alternatives to exemestane
- every medicine labeled for the same conditions