Endoxifen
tamoxifen metabolite
What it is4-hydroxy-N-desmethyltamoxifen, formed by CYP2D6, roughly a hundred times more potent at the estrogen receptor than tamoxifen.
Why it mattersResponsible for activity; tamoxifen itself is nearly inactive.
What it changesCYP2D6 poor metabolizers and strong CYP2D6 inhibitors such as fluoxetine and paroxetine therefore blunt tamoxifen’s benefit.
Used for
- breast cancer (active metabolite of tamoxifen)
NO BOXED WARNINGS
Principal riskLittle in its own right; see the parent drug
Classes and tags
Open Endoxifen in the interactive console ↗
Self-check
- Which enzyme forms endoxifen?
CYP2D6. - How can paroxetine affect tamoxifen benefit?
Blunt it by reducing endoxifen formation.