Ans. is 'b' i.e., SERM o Tamoxifen is a selective estrogen receptor modulator (SERM).SELECTIVE ESTROGEN RECEPTOR MODULATION (SERMs)1. Tamoxifen citrate# It is a nonsteroidal compound# It has both estrogen antagonist as well as partial agonist activity -Tamoxifen (selective estrogen receptor modulator)o Sites on which it acts as estrogen antagonisti) Breast carcinomaii) Blood vesselsiii) Some peripheral sitesSite at which it acts as partial agonisti) Uterus - Causes proliferation of endometriumii)Bone - Improves bone mass d/t its antiresorptive effectiii) Lipid profile - Decrease LDL without any change in HDL (| risk of coronary artery disease)# Incresed risk of deep vein thrombosis.Tamoxifen is the standard hormonal treatment of breast cancer in both pre and postmenopausal women, though aromatase inhibitors are now becoming choice.Improvement in bone mass (due to antiresorptive effect) and in lipid profile are the benefits of tamoxifen.It has biphasic t1/2 - (10 hours and 7 days).2. Toremifene (Has been added to 6th/e of KDT)Newer tamoxifen congener with similar action and uses.3. RaloxifeneThis SERM is different from tamoxifen in that it has antagonistic action on endometrium (Tamoxifen has partial agonistic action) - No risk of endometrial proliferation amd carcinoma.All other actions are same.It is mainly used as first line drug for prevention and treatment of osteoprorosis.4. QrmeloxifeneIt also has antagonistic action on endometrium - has been approved for dysfunctional uterine bleeding.o Fulvestrant - It is a selective estrogen receptor down regulators (SERDs) or pure estrogen antagonist. In contrast to tomoxifen, it inhibits estrogen receptor (ER) dimerization so that ER interaction with DNA is prevented and receptor degradation is enhanced. The ER is thus down regulated resulting in more complete suppresion of ER responsive gene function. It is used for ER positive metastatic breast cancer.