What it is
A selective estrogen receptor modulator (SERM) available as oral tablets or oral solution.
How it works
Acts as a competitive estrogen receptor antagonist in breast tissue while exhibiting partial agonist activity in other tissues such as bone and endometrium.
Where it's used
Used in treatment and prevention of hormone-receptor-positive breast cancer. Off-label uses include gynecomastia and hypogonadism management.
FDA-approved use
Treatment of metastatic breast cancer, adjuvant treatment of breast cancer, and reduction in breast cancer incidence in high-risk women.
Tracking it
Tamoxifen is oral, which makes consistency the whole game — a simple daily check-off with a reminder beats memory every time. with a half-life of about 7 days (168 h), a dose log also lets a tracker model the relative amount still in your system between doses.
Source
OpenFDA
Last reviewed 2026-06-11