Singapore Drugs Database

Description

Conjugated estrogens, or Conjugated Equine Estrogens (CEEs) are composed of a mixture of the water-soluble salts of sulfate esters from estrone, equilin, 17 α-dihydroequilin, and other related steroids that are purified from pregnant horse urine. Available as the product Premarin (FDA), this combination of equine-derived estrogenic compounds is indicated for the following conditions: treatment of moderate to severe vasomotor symptoms and vulvovaginal atrophy associated with menopause; hypoestrogenism due to hypogonadism, castration or primary ovarian failure; palliation of metastatic breast cancer; palliation of advanced androgen-dependent carcinoma of the prostate; and for prevention of postmenopausal osteoporosis. All estrogen products mimic the effects of endogenous estrogens in the body which are responsible for the development and maintenance of the female reproductive system and secondary sexual characteristics. Estrogens act by binding to estrogen receptors on a wide variety of tissues in the body and modulating the pituitary secretion of the gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH) through a negative feedback mechanism. Prior to menopause, the primary source of estrogen is the ovarian follicle, which secretes 70-500 micrograms of estradiol daily, depending on the phase of the menstrual cycle. However, once a woman stops ovulating there is a sharp decline in the production of progesterone and estradiol by the ovaries and a consequent fluctuation in LH and FSH due to a lack of feedback control. This shift in hormone production is largely responsible for many of the symptoms experienced during and after menopause and includes hot flashes and other vasomotor symptoms, painful intercourse, vaginal dryness, and vulvovaginal atrophy. These symptoms are able to be reduced by replacing many of the hormones lost during and following menopause with synthetic or naturally occurring forms, in a therapy known as Hormone Replacement Therapy (HRT). Pharmacologic estrogen products are available in a variety of formats. Although many of them contain several compounds in common (such as the estrogen derivatives sodium estrone sulfate and sodium equilin sulfate), they vary by their original source (such as horse-, human-, or plant-derived), and the remaining mixture of estrogenic derivatives. Conjugated Equine Estrogens (CEEs) are derived from the urine of pregnant mares and contain a blend of at least 10 estrogen derivatives. Marketed under the brand name Premarin, CEEs are the most frequently used form of conjugated estrogens. There is currently no generic form of CEEs available as a detailed analytical characterization of the active ingredients or of their estrogenic activity is not available at this time. Conjugated estrogens are also available in a plant-derived synthetic form that replicates the naturally occurring, horse-derived forms. Available as either "Synthetic Conjugated Estrogens, A" containing 9 estrogen derivatives (available as Cenestin) or as "Synthetic Conjugated Estrogens, B" containing 10 estrogen derivatives (available as Enjuvia), these products are isolated as precursors from yam or soy plants and then chemically modified to mimic the products available in their naturally occurring form.