Two medicines, side by side
Exemestane vs letrozole
Exemestane and letrozole are both labeled for breast cancer. Drugs@FDA records approvals of exemestane since 1999 and of letrozole since 1997. Pharmacies paid $0.748 per exemestane 25 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: Exemestane, “Aromatase is the principal enzyme that converts androgens to estrogens both in pre- and postmenopausal women.”; Letrozole, “The growth of some cancers of the breast is stimulated or maintained by estrogens.”
Check it at the source: the exemestane FDA label on DailyMed (effective September 12, 2024); the letrozole FDA label on DailyMed (effective June 11, 2026).
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 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 (Exemestane label of September 12, 2024, Letrozole label of June 11, 2026); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do exemestane and letrozole differ on the record?
How each works, in its label's words: Exemestane, “Aromatase is the principal enzyme that converts androgens to estrogens both in pre- and postmenopausal women.”; 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: Exemestane, “12.3 Pharmacokinetics Following oral administration to healthy postmenopausal women, plasma concentrations of …”; Letrozole, “Letrozole’s terminal elimination half-life is about 2 days and steady-state plasma concentration after daily 2.5 mg …”
Generics: exemestane since 2011; letrozole since 2008 (Drugs@FDA).
| Exemestane | Letrozole | |
|---|---|---|
| Labeled for | Breast cancer | Breast cancer |
| Pharmacologic class | Aromatase Inhibitor | Aromatase Inhibitor |
| 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. | The growth of some cancers of the breast is stimulated or maintained by estrogens. |
| 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. | 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) | October 21, 1999 | July 25, 1997 |
| First generic approved | April 1, 2011 | December 24, 2008 |
| Generic labelers (NDC) | 10 labelers | 19 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.748 per tablet (Exemestane 25 mg tablet) | $0.145 per tablet (Letrozole 2.5 mg tablet) |
| 12-month price change | +7% | +12% |
| Boxed warning | No | No |
| Shortage now | No current entry | No current entry |
| Recalls recorded | 0 | 1 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 21,298 | 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 exemestane
- every medicine labeled for the same conditions