🔴 Mechanism of Action 🔴

🔺1. Antiestrogen :- e.g.Clomiphene citrate :-
It binds with both ER alpha and ER beta receptor.
Trans isomer i.e. enclomiphene acts as a pure ANTAGONIST in all human tissues.
Cis isomer i.e. zuclomiphene and racemate display weak antagonistic action in rats.

🔺2.Selective estrogen receptor down-regulator :- e.g.Fulvestrant :- It inhibits ER Dimerization so that ER interaction with DNA is prevented and receptor degradation is enhanced.

🔺3. Selective Estrogen receptor modulator (SERMs) :-
These are drugs which exert estrogenic as well as sntiestrogenic action in a tissue selective manner.
That ligand binding could change the configuration of ER in multiple ways allowing interaction with different coactivators and corepressors in a tissue specific manner has paved the way for development of compounds with unique profile if agonistic and antagonistic actions in different tissues.
e.g. Tamoxifen citrate,
Toremifene, Ralixifene.

🔺4. Aromatase Inhibitors :-

Aromatization of 'A' ring of Testosterone and Androstenedione is the final and key step in the production of estrogens ( estradiol and /or estrone) in the body. In addition to circulating hormone, locally produced estrogens appear to play an important role in the development of breast cancer. So, Aromatse inhibitors are widely used now in the treatment of Breast cancer (Exemestane) .
e.g. Letrozole, Anastrozole, Exemestane.

🔴ADRS OF ANTIESTROGEN🔴
polycystic ovaries
Multiple preganncy
Hot flashes
Gastric upset
Vertigo
Allergic dermattits
Ovarian tumour