Tamoxifen is a triphenylethylene SERM. Competitively binds oestrogen receptor alpha (ERα) with high affinity. Tissue-selective: acts as ER antagonist in breast tissue (blocking oestrogen-driven proliferation) but as partial ER agonist in bone and uterus. Metabolised by CYP2D6 to the active 4-hydroxytamoxifen and endoxifen, which have 30–100× higher ERα affinity than tamoxifen itself. Also used in research to block gynecomastia (ER antagonism in breast tissue) during androgen research protocols.
Also Known As
Nolvadex, TAM, ICI 46,474
Compound Class
Selective Oestrogen Receptor Modulator (SERM)
Molecular Formula
C₂₆H₂₉NO
Molecular Weight
371.51 Da
CAS Number
10540-29-1
Half-Life
~5–7 days (active metabolite endoxifen ~10 days)
Research Applications
Breast Cancer / ER-positive Tumour Research
Tamoxifen is the longest-studied endocrine therapy for ER+ breast cancer — 40+ years of clinical data. ERα antagonism blocks oestradiol-driven transcription of proliferative genes. ATAC, NSABP, and multiple RCTs define tamoxifen as the reference ER+ breast cancer research compound.
Gynecomastia Research
ERα antagonism in breast tissue blocks oestrogen-driven ductal proliferation. Dose-response studies in pubertal and adult gynecomastia models. Reference comparator against aromatase inhibitors for breast tissue-specific ER blockade.
HPG Axis / PCT Research
Like clomiphene, tamoxifen blocks hypothalamic ER negative feedback and raises LH/FSH. Used in HPG axis recovery research, post-cycle models. Slower onset than clomiphene but longer duration due to extended half-life.
Bone / Uterine ER Agonism Research
Tamoxifen partial agonism at ERα in bone (increased BMD) and uterus (endometrial proliferation risk at high dose) is a key SERM tissue-selectivity research model. Contrasting effects in different tissues make it an essential SERM pharmacology reference.
Key Research Data
Study / Source
Key Findings
ATAC Trial 2002 Lancet
N=9,366 postmenopausal ER+ BC: tamoxifen vs anastrozole — definitive comparative data for ERα antagonism in breast cancer research
Early Breast Cancer Trialists 2011 Lancet
Meta-analysis: 5 years tamoxifen halves recurrence rate during treatment and years 5-14, mortality benefit confirmed
Czekalski et al. Gynecomastia
Tamoxifen 20mg/day resolved gynecomastia in 78% vs 41% placebo — dose-response data for tissue-selective ER blockade
Specifications
Format
Oral tablet — 20mg per tablet
Purity
≥99% HPLC
Identity
MS confirmed
Storage
Room temperature, protect from moisture
Metabolism
CYP2D6 → 4-OH-tamoxifen → endoxifen (active)
Frequently Asked Questions
What is Tamoxifen (Nolvadex)?
Tamoxifen (Nolvadex) is a Selective Oestrogen Receptor Modulator (SERM). Tamoxifen is a triphenylethylene SERM. Competitively binds oestrogen receptor alpha (ERα) with high affinity. Tissue-selective: acts as ER antagonist in breast tissue (blocking oestrogen-driven proliferation) but as partial ER agonist in bone and ute…
How does Tamoxifen work in research models?
Tamoxifen is the longest-studied endocrine therapy for ER+ breast cancer — 40+ years of clinical data. ERα antagonism blocks oestradiol-driven transcription of proliferative genes. ATAC, NSABP, and multiple RCTs define tamoxifen as the reference ER+ breast cancer research compoun…
What makes Tamoxifen different from similar compounds?
ERα antagonism in breast tissue blocks oestrogen-driven ductal proliferation. Dose-response studies in pubertal and adult gynecomastia models. Reference comparator against aromatase inhibitors for breast tissue-specific ER blockade….
Does QSC ship Tamoxifen to the USA?
Yes. QSC Tamoxifen ships domestically across the USA and internationally to EU, UK, Canada, and Australia. Every batch carries a Janoshik third-party COA confirming ≥99% HPLC purity and MS identity verification.
