Two medicines, side by side
Anastrozole vs letrozole
Anastrozole and letrozole are both labeled for breast cancer. Drugs@FDA records approvals of anastrozole since 1995 and of letrozole since 1997. Pharmacies paid $0.142 per anastrozole 1 mg tablet and $0.145 per letrozole 2.5 mg tablet (NADAC, October 7, 2026); the strengths differ, so the two prices are not like for like. How each works, in its label's words: Anastrozole, “The growth of many cancers of the breast is stimulated or maintained by estrogens.”; Letrozole, “The growth of some cancers of the breast is stimulated or maintained by estrogens.”
Check it at the source: the anastrozole FDA label on DailyMed (effective March 2, 2026); the letrozole FDA label on DailyMed (effective June 11, 2026).
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 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
Source: FDA drug labels via openFDA (Anastrozole label of March 2, 2026, Letrozole label of June 11, 2026); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do anastrozole and letrozole differ on the record?
How each works, in its label's words: Anastrozole, “The growth of many cancers of the breast is stimulated or maintained by estrogens.”; Letrozole, “The growth of some cancers of the breast is stimulated or maintained by estrogens.”
Both are in FDA's class aromatase inhibitors.
Half-life, in each label's words: Anastrozole, “The mean elimination half-life of anastrozole is 50 hours.”; Letrozole, “Letrozole’s terminal elimination half-life is about 2 days and steady-state plasma concentration after daily 2.5 mg …”
Generics: anastrozole since 2010; letrozole since 2008 (Drugs@FDA).
| Anastrozole | Letrozole | |
|---|---|---|
| Labeled for | Breast cancer | Breast cancer |
| Pharmacologic class | Aromatase Inhibitor | Aromatase Inhibitor |
| How it works (label) | The growth of many cancers of the breast is stimulated or maintained by estrogens. | The growth of some cancers of the breast is stimulated or maintained by estrogens. |
| Half-life (label) | The mean elimination half-life of anastrozole is 50 hours. | 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. |
| Earliest approval on file (Drugs@FDA) | December 27, 1995 | July 25, 1997 |
| First generic approved | June 28, 2010 | December 24, 2008 |
| Generic labelers (NDC) | 24 labelers | 19 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.142 per tablet (Anastrozole 1 mg tablet) | $0.145 per tablet (Letrozole 2.5 mg tablet) |
| 12-month price change | +3% | +12% |
| Boxed warning | No | No |
| Shortage now | No current entry | No current entry |
| Recalls recorded | 4 | 1 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 36,521 | 61,238 |
| 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)
What next?
- Alternatives to anastrozole
- every medicine labeled for the same conditions