tamoxifen citrate
Meaning of tamoxifen citrate: A tablet that blocks estrogen in breast tissue while imitating it elsewhere, which explains both its benefits and its risks.
Definition of tamoxifen citrate
Tamoxifen citrate is a tablet that interferes with estrogen signaling in breast tissue, used for breast cancers whose cells carry estrogen receptors. It occupies the receptor so estrogen cannot switch it on, slowing growth that depends on the hormone. It is taken after surgery to reduce the chance of recurrence, in advanced disease, and to lower risk in people at high risk.
Why does it act differently in different tissues?
It belongs to a class known as selective estrogen receptor modulators. The drug binds the same receptor everywhere, but the shape it forces the receptor into recruits different partner proteins in different tissues, so the outcome varies by site. In the breast the result is blockade, which is the therapeutic effect. In bone the result is mild stimulation, which helps preserve density after menopause. In the lining of the uterus it is also mild stimulation, which is where the main risk comes from. One drug therefore behaves as an antiestrogen in one organ and as a weak estrogen in another.
Who is it used for?
| Setting | Purpose |
|---|---|
| After surgery for hormone receptor positive breast cancer | Reduces recurrence and death over years of treatment |
| Before or after menopause | Usable in both, unlike aromatase inhibitors, which work only after menopause |
| Breast carcinoma in situ | Lowers the chance of further disease in either breast |
| High risk without cancer | Risk reduction in selected people |
| Breast cancer in men | The standard hormone treatment |
What are the main adverse effects?
Hot flashes are the commonest, along with vaginal dryness or discharge, irregular periods and mood changes. The serious effects are less common but well defined: blood clots in the legs and lungs, thickening of the lining of the uterus with a raised risk of endometrial cancer, and cataracts. New vaginal bleeding during treatment is investigated rather than assumed to be a side effect.
Why does metabolism matter?
The tablet is largely inactive as swallowed. A liver enzyme converts it into the form that does the work, and people vary in how much of that enzyme they have. Drugs that block the same enzyme, including certain antidepressants, reduce the conversion, which is why prescribing decisions take other medicines into account.
Also known as
Used in a sentence
Tamoxifen citrate was continued as adjuvant hormone therapy for estrogen receptor positive breast cancer.
Good to know
Tamoxifen blocks estrogen in breast tissue but mildly stimulates the lining of the uterus, so new vaginal bleeding during treatment is investigated rather than treated as an expected effect.