Compare · Aromatase inhibitor
Anastrozole vs Letrozole
Both are aromatase inhibitor compounds. Here's how they line up on the evidence — graded the same way.
| Anastrozole | Letrozole | |
|---|---|---|
| Evidence | Strong human | Strong human |
| Class | Aromatase inhibitor | Aromatase inhibitor |
| Summary | Anastrozole is a non-steroidal aromatase inhibitor — a prescription breast-cancer drug, not a peptide — with strong trial evidence in postmenopausal women and a separate, unstudied off-label use by men to suppress estrogen. It is banned in sport at all times. | Letrozole is an oral, nonsteroidal third-generation aromatase inhibitor — an FDA-approved breast-cancer and (off-label) fertility drug, not a peptide. Bodybuilders use it off-label to suppress estrogen, an unapproved and unstudied practice that is banned in sport (WADA S4) and can be genuinely harmful when estrogen is crashed. |
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Anastrozole
Anastrozole, sold as Arimidex, is a non-steroidal aromatase inhibitor: a prescription breast-cancer drug that lowers the body's estrogen by blocking the enzyme that makes it. It is important to be precise about what anastrozole is and is not. It is not an anabolic-androgenic steroid, not a SERM…
Letrozole
Letrozole, sold as Femara, is an oral, nonsteroidal third-generation aromatase inhibitor (AI) — a legitimate, well-studied drug with a strong evidence base in both oncology and fertility medicine. It is important to be precise about what it is: letrozole is not a peptide, not a SERM (selective…