SHEET /vs/tamoxifen-vs-letrozole · COMPARISON
Tamoxifen vs Letrozole: what is the difference?
How they differ
from source
Tamoxifen and letrozole both deprive hormone-sensitive breast cancer of estrogen, from opposite ends. Tamoxifen blocks the estrogen receptor in breast tissue, so the hormone is present but cannot act there, while letrozole blocks aromatase, the enzyme that makes estrogen, so less of it exists at all. That is why letrozole is used after menopause, when aromatase in fat tissue is the main source, while tamoxifen works before and after it. They look nothing alike: tamoxifen, C26H29NO at 371.5, is built on a triphenylethylene skeleton, and letrozole, C17H11N5 at 285.3, carries a triazole ring and two nitrile groups. Both are prescription medicines, sold as Nolvadex and Femara.
Side by side
| Tamoxifen | Letrozole | |
|---|---|---|
| Formula | C26H29NO | C17H11N5 |
| Molecular weight | 371.5 g/mol | 285.3 g/mol |
| Family | Cancer medicines | Cancer medicines |
| Everyday group | Prescription medicine | Prescription medicine |
| Functional groups | Aromatics, Ethers | Aromatics |
| GHS signal wordThe supplier-filed hazard label, not a statement about ordinary use. | Danger | Danger |
| CAS number | 10540-29-1 | 112809-51-5 |
| PubChem CID | 2733526 | 3902 |
Common questions
- What is the difference between Tamoxifen and Letrozole?
- Tamoxifen and letrozole both deprive hormone-sensitive breast cancer of estrogen, from opposite ends. Tamoxifen blocks the estrogen receptor in breast tissue, so the hormone is present but cannot act there, while letrozole blocks aromatase, the enzyme that makes estrogen, so less of it exists at all. That is why letrozole is used after menopause, when aromatase in fat tissue is the main source, while tamoxifen works before and after it.
- Is Tamoxifen bigger than Letrozole?
- Tamoxifen is the heavier molecule, 371.5 g/mol against 285.3 g/mol for Letrozole. Tamoxifen is C26H29NO and Letrozole is C17H11N5.