Estradiol

0.75 mg, 1.25 mg, 1.5 mg, 1.75 mg, 2.5 mg, 3 mg

Estradiol is the principal intracellular human estrogen and is substantially more active than its metabolites, estrone and estriol, at the cellular level. Estradiol can be obtained from natural sources or prepared synthetically. There is no evidence that 'natural' estrogens are more or less efficacious or safe than 'synthetic' estrogens. Due to almost complete first-pass metabolism, estradiol must be given in a micronized oral dosage form to ensure therapeutic effect. Esterification of estradiol to estradiol cypionate or valerate increases the parenteral duration of action of estradiol to allow for parenteral intramuscular administration. Estradiol is primarily used to prevent osteoporosis and relieve vasomotor and genitourinary symptoms associated with menopause (natural or surgical), for postmenopausal osteoporosis prevention, and is also used to treat female hypogonadism and other abnormalities of female gonadotropin dysfunction. Various estrogen products have been marketed in the U.S. since 1938. Estradiol is available in many dosage forms, including oral tablets, transdermal systems, topical emulsions, topical gels, topical sprays, vaginal creams, vaginal rings, and parenteral depot injections. Vaginal therapies are preferred in postmenopausal women with exclusive genitourinary symptoms, due to lower systemic absorption/exposure with most of these dosage forms. Many estradiol products have been FDA-approved since the 1990's, in accordance with the FDA's guidance to provide efficacious low-dose estrogen therapies in alternate drug delivery systems.

The primary source of estrogens in premenopausal women is the ovary, which normally secretes 0.07 to 0.5 mg of estradiol daily, depending on the phase of the menstrual cycle. Once estrogens enter the cells of responsive tissues (e.g., female organs, breasts, hypothalamus, pituitary), they increase the rate of synthesis of DNA, RNA, and some proteins. The secretion of gonadotropin-releasing hormone by the hypothalamus is reduced during estrogen administration, causing reduction in follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary. Exogenous estrogens elicit all of the actions of endogenous estrogens. Estrogens are responsible for the growth and development of female sex organs and the maintenance of sex characteristics including growth of axillary and pubic hair and shaping of body contours and skeleton. At the cellular level, estrogens increase cervical secretions, cause proliferation of the endometrium, and increase uterine tone. Paradoxically, prolonged administration of estrogen can shrink the endometrium. During the preovulatory or non ovulatory phase of the menstrual cycle, withdrawal of estrogen can initiate menstruation; in the ovulatory phase, the decrease in progesterone secretion is the more significant factor causing menstruation. In post-menopausal use, amenorrhea occurs in most women within several months of oral estrogen use. Estrogens appear to prevent osteoporosis associated with the onset of menopause. Estrogens generally have a favorable effect on blood lipids, reducing LDL- and increasing HDL-cholesterol concentrations on average, by 15%. Serum triglycerides increase with estrogen administration. Estrogens increase the rate of synthesis of many proteins, including thyroid binding globulin and several clotting factors. Estrogens reduce levels of antithrombin III, and increase platelet aggregation. Estrogens also enhance sodium and fluid retention. In men with advanced prostate cancer, estrogens exert their effect by inhibition of the hypothalamic-pituitary axis through negative feedback. This results in decreased secretion of luteinizing hormone (LH). Decreased testosterone production from the Leydig cells in the testes occurs, which may decrease tumor growth and lower prostate specific antigen (PSA) levels. Improvement in bone metastasis may also occur.

Do not use estrogens in patients with severe hepatic disease of any type. In postmenopausal women with end stage renal disease (ESRD) receiving maintenance hemodialysis, total estradiol serum levels are higher than in normal subjects at baseline and following oral doses of estradiol. Therefore, conventional transdermal estradiol doses used in individuals with normal renal function may be excessive for postmenopausal women with ESRD receiving maintenance hemodialysis. Recommended initial doses of estrogen therapy in this population are usually one-eighth to one-tenth the doses used for adult replacement, and vary depending on the formulation used. Do not use estradiol products in patients with a known hypersensitivity to any of the specific product ingredients; estradiol is contraindicated in patients with known anaphylactic reactions or history of angioedema to the drug. Cases of both anaphylactic reactions and angioedema have been reported in patients taking estrogens, including estradiol. Events have developed in minutes and have required emergency medical treatment. Exogenous estrogens may also induce or exacerbate symptoms of angioedema, particularly in women with hereditary angioedema, which can be hormonally sensitive. Estradiol products are contraindicated in patients with a known or suspected estrogen-dependent neoplasm, including breast cancer. All women taking estrogen with or without a progestin should receive an annual clinical breast examination, perform monthly self-examinations, annual pelvic examination and have regular mammograms as recommended by their health care professional based on patient age, risk factors, and prior mammogram results. Estrogen therapy is contraindicated in patients with known vaginal cancer, cervical cancer, uterine cancer, or other estrogen-dependent malignancies. There is an association of unopposed estrogen therapy and endometrial cancer in women with an intact uterus. Adding a progestin to estrogen therapy has been shown to reduce the risk of endometrial hyperplasia, which may be a precursor to endometrial cancer. Clinical surveillance of all women using estrogen-alone or estrogen plus progestin therapy is important. Estrogens are contraindicated in patients with an active or past history of thrombophlebitis, thromboembolism, thromboembolic disease, stroke, or myocardial infarction (MI). An increased risk of cerebrovascular disease (stroke) and deep venous thrombosis (DVT) has been reported with unopposed estrogen therapy. An increased risk of thromboembolism, including pulmonary embolism (PE), DVT, stroke and myocardial infarction (MI) has been reported with estrogen plus progestin hormone replacement therapy (HRT).

Estrogens are contraindicated during pregnancy. There is no known approved indication for the use of estrogens during pregnancy. There appears to be little or no increased risk of birth defects in children born to women who have used estrogens and progestins from oral contraceptives inadvertently during early pregnancy. Estradiol and other estrogens freely cross the placenta to the fetus. Increased risk of a wide variety of fetal abnormalities, including modified development of sexual organs, cardiovascular anomalies and limb defects, have been reported following the continued use of estrogens in pregnant women. In any patient in whom pregnancy is suspected, pregnancy should be ruled out before continuing estrogen use.

Caution should be used if a breast-feeding mother is receiving estradiol for hormone replacement. Estrogen administration to nursing women is generally avoided during lactation as estrogens have been shown to decrease the quantity and quality of the breast milk. Detectable amounts of estrogens have been identified in the milk of mothers receiving estradiol and other estrogens.