| Indication | For the treatment of moderate to severe vasomotor symptoms associated with the menopause, atrophic vaginitis, osteoporosis, hypoestrogenism due to hypogonadism, castration, primary ovarian failure, breast cancer (for palliation only), and Advanced androgen-dependent carcinoma of the prostate (for palliation only) |
| Pharmacodynamics | Conjugated estrogens, a mixture of the water soluble salts of sulfate esters from estrone, equilin, 17 α-dihydroequilin, and other related steroids, may be derived from pregnant equine urine or yam and soy plants. Estrogens are important in the development and maintenance of the female reproductive system and secondary sex characteristics. They promote growth and development of the vagina, uterus, and fallopian tubes, and enlargement of the breasts. Indirectly, they contribute to the shaping of the skeleton, maintenance of tone and elasticity of urogenital structures, changes in the epiphyses of the long bones that allow for the pubertal growth spurt and its termination, growth of axillary and pubic hair, and pigmentation of the nipples and genitals. Decline of estrogenic activity at the end of the menstrual cycle can bring on menstruation, although the cessation of progesterone secretion is the most important factor in the mature ovulatory cycle. However, in the preovulatory or nonovulatory cycle, estrogen is the primary determinant in the onset of menstruation. Estrogens also affect the release of pituitary gonadotropins. The pharmacologic effects of conjugated estrogens are similar to those of endogenous estrogens. |
| Mechanism of action | Estrogens enter the cells of responsive tissues (e.g., female organs, breasts, hypothalamus, pituitary) where they interact with a protein receptor, subsequently increasing the rate of synthesis of DNA, RNA, and some proteins. Estrogens decrease the secretion of gonadotropin-releasing hormone by the hypothalamus, reducing the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary. |
| Absorption | Well absorbed |
| Volume of distribution | Not Available |
| Protein binding | 90% bound to plasma proteins |
| Metabolism | Hepatic |
| Route of elimination | Estradiol, estrone, and estriol are excreted in the urine, along with glucuronide and sulfate conjugates. Exogenous estrogens are metabolized in the same manner as endogenous estrogens. |
| Half life | 7.4 hours |
| Clearance | Not Available |
| Toxicity | Nausea and vomiting |