Two medicines, side by side
Letrozole vs tamoxifen
Letrozole and tamoxifen are both labeled for breast cancer. Drugs@FDA records approvals of letrozole since 1997 and of tamoxifen since 1977. Pharmacies paid $0.145 per letrozole 2.5 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, letrozole is an aromatase inhibitor and tamoxifen an estrogen agonist/antagonist.
Check it at the source: the letrozole FDA label on DailyMed (effective June 11, 2026); the tamoxifen FDA label on DailyMed (effective December 18, 2025).
Highlights of the letrozole record
Letrozole (Femara) · label of June 11, 2026
Used for
From the label: indicationsFemara is an aromatase inhibitor indicated for: Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer. ( 1.1 ) Extended adjuvant treatment of postmenopausal women with early breast cancer who have received prior standard adjuvant tamoxifen therapy. ( 1.2 ) First and second-line treatment of postmenopausal women with hormone receptor positive or unknown advanced breast cancer. […]
On the market
- Earliest approval on file
- July 25, 1997
- Generic labelers
- 19 labelers
- Pharmacy cost
- $0.145 per tablet
Supply and safety
- Shortage
- No current entry
- Recalls
- 1
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 (Letrozole label of June 11, 2026, Tamoxifen label of December 18, 2025); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do letrozole and tamoxifen differ on the record?
In FDA's classes, letrozole is an aromatase inhibitor and tamoxifen an estrogen agonist/antagonist.
Half-life, in each label's words: Letrozole, “Letrozole’s terminal elimination half-life is about 2 days and steady-state plasma concentration after daily 2.5 mg …”; 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: letrozole since 2008; tamoxifen since 2003 (Drugs@FDA).
| Letrozole | Tamoxifen | |
|---|---|---|
| Labeled for | Breast cancer | Breast cancer |
| Pharmacologic class | Aromatase Inhibitor | Estrogen Agonist/Antagonist |
| How it works (label) | The growth of some cancers of the breast is stimulated or maintained by estrogens. | n/a |
| Half-life (label) | Letrozole’s terminal elimination half-life is about 2 days and steady-state plasma concentration after daily 2.5 mg dosing is reached in 2-6 weeks. | 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) | July 25, 1997 | December 30, 1977 |
| First generic approved | December 24, 2008 | February 20, 2003 |
| Generic labelers (NDC) | 19 labelers | 10 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.145 per tablet (Letrozole 2.5 mg tablet) | $0.277 per tablet (Tamoxifen 20 mg tablet) |
| 12-month price change | +12% | -2% |
| Boxed warning | No | Yes |
| Shortage now | No current entry | No current entry |
| Recalls recorded | 1 | 0 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 61,238 | 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?
Letrozole label, drug interactionsDRUG INTERACTIONS Tamoxifen Coadministration of Femara and tamoxifen 20 mg daily resulted in a reduction of letrozole plasma levels of 38% on average (Study P015).
Letrozole label, warnings and precautionsResults of a safety study to evaluate safety in the adjuvant setting comparing the effect on lumbar spine (L2-L4) BMD of adjuvant treatment with letrozole to that with tamoxifen showed at 24 months a median decrease in lumbar spine BMD of 4.1% in the letrozole arm compared to a median increase of 0.3% in the tamoxifen arm (difference = 4.4%) ( P < 0.0001) [ s ee Adverse Reactions (6)].
Tamoxifen label, drug interactionsTamoxifen reduced letrozole plasma concentrations by 37%.
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 letrozole
- every medicine labeled for the same conditions