PREMARIN

Indications

• Menopausal symptoms
• Vulvar and vaginal atrophy
• Prevention of osteoporosis in postmenopausal women
• Hypoestrogenism due to hypogonadism or castration

Dosage

Children: Conjugated estrogens are not typically indicated for use in the pediatric population. Refer to specialized resources for any off-label use.

Adults: Refer to the BNF for specific dosing guidelines, as doses may vary based on the indication and patient-specific factors.

Mechanism of action

Conjugated estrogens exert their effects primarily through binding to estrogen receptors, leading to the activation of estrogen-responsive genes. This binding triggers a cascade of biological responses that promote the development and maintenance of female reproductive tissues, regulation of the menstrual cycle, and other systemic effects such as bone density maintenance and modulation of cholesterol levels.

Pharmacodynamics

The pharmacodynamics of conjugated estrogens involve their role in modulating gene expression within estrogen-responsive tissues. They help to alleviate symptoms associated with menopause, such as hot flashes and vaginal dryness, and play a critical role in bone health by inhibiting osteoclast activity, thus reducing bone resorption and helping to prevent osteoporosis.

Pharmacokinetics

Following oral administration, conjugated estrogens are absorbed through the gastrointestinal tract. They undergo first-pass metabolism in the liver, which can affect their bioavailability. The half-life of conjugated estrogens varies, but they generally have a half-life of several hours. They are metabolized primarily in the liver and excreted in urine. The pharmacokinetics can be influenced by factors such as age, liver function, and concurrent medications.

Contra-indications

• Known hypersensitivity to conjugated estrogens or any of the excipients
• Estrogen-dependent neoplasms, including breast cancer
• Undiagnosed abnormal genital bleeding
• Active or past venous thromboembolic disorders
• Severe liver dysfunction or disease
• Pregnancy

Adverse effects

• Nausea
• Headache
• Breast tenderness
• Abdominal cramps
• Bloating
• Mood changes
• Increased risk of thromboembolic events
• Hypertension
• Cholestatic jaundice
• Gallbladder disease

Interactions

• Anticoagulants may have altered effects
• Certain anticonvulsants may reduce efficacy of estrogen therapy
• Rifampicin and other enzyme inducers may decrease effectiveness
• St. John's Wort may decrease hormone levels

Precautions

• Monitor patients for signs of thromboembolic disorders
• Assess risk factors for cardiovascular disease
• Evaluate liver function before and during treatment
• Consider individual patient history of breast cancer or other estrogen-sensitive conditions

Pregnancy

Conjugated estrogens are contraindicated in pregnancy due to risk of fetal harm.

Breast-feeding

Conjugated estrogens may be excreted in breast milk; use with caution in breastfeeding women.

Storage

Store at room temperature, away from light and moisture. Keep out of reach of children.

Formulations

• Oral tablets
• Injectable forms

Indications

• Hormone replacement therapy for menopausal symptoms
• Management of menopausal symptoms such as hot flashes and vaginal atrophy
• Treatment of hypoestrogenism
• Contraception in combination with progestins
• Management of estrogen receptor-positive breast cancer in postmenopausal women

Dosage

Children: Refer to the BNF for Children for appropriate dosing information for pediatric patients.

Adults: Refer to the BNF for specific dosing recommendations based on the formulation and clinical condition being treated.

Mechanism of action

Estrogens act by binding to estrogen receptors located on diverse tissues throughout the body. This binding modulates the secretion of pituitary gonadotropins, specifically luteinizing hormone (LH) and follicle stimulating hormone (FSH), through a negative feedback mechanism. In premenopausal women, estrogens are predominantly secreted by ovarian follicles, and their levels fluctuate during the menstrual cycle. Following menopause, the decline in estrogen production leads to various symptoms which can be alleviated by estrogen replacement.

Pharmacodynamics

The pharmacodynamic effects of estrogens include the regulation of reproductive functions, enhancement of bone density, modulation of cardiovascular health, and maintenance of skin and mucosal integrity. Estrogens exert their effects through genomic pathways that alter gene expression, ultimately influencing tissue growth and function.

Pharmacokinetics

Estrogens are absorbed well from the gastrointestinal tract and undergo extensive first-pass metabolism in the liver. They have a high volume of distribution and are primarily metabolized in the liver, leading to the formation of various metabolites. Estrogens are eliminated through urine and feces, with a half-life that varies depending on the specific estrogen used. Additionally, their pharmacokinetics can be influenced by factors such as age, body weight, and the presence of liver disease.

Contra-indications

• Known or suspected pregnancy
• Active liver disease
• History of thromboembolic disorders
• Hormone-sensitive malignancies
• Undiagnosed abnormal uterine bleeding

Adverse effects

• Nausea
• Vomiting
• Breast tenderness
• Headache
• Mood changes
• Weight gain
• Increased risk of thromboembolic events

Interactions

• Anticonvulsants may reduce estrogen effectiveness
• Antibiotics may alter gut flora and affect estrogen metabolism
• Corticosteroids may have increased effects when used with estrogens

Precautions

• Monitor for signs of thromboembolic events
• Use with caution in patients with a history of depression
• Caution in patients with hypertension

Pregnancy

Estrogens are contraindicated in pregnancy due to potential risks to the fetus.

Breast-feeding

Estrogens may be excreted in breast milk and could affect milk production.

Storage

Store in a cool, dry place, away from direct sunlight and out of reach of children.

Formulations

• Tablets
• Transdermal patches
• Injectable forms
• Topical creams and gels

Mechanism of action

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). The principal pharmacologic effects of conjugated estrogens are similar to those of other natural and synthetic estrogens. Estrogens have an important role in the reproductive, skeletal, cardiovascular, and central nervous systems in women, and act principally by regulating gene expression. Biologic response is initiated when estrogen binds to a ligand-binding domain of the estrogen receptor resulting in a conformational change that leads to gene transcription through specific estrogen response elements (ERE) of target gene promoters; subsequent activation or repression of the target gene is mediated through 2 distinct transactivation domains (ie, AF-1 and AF-2) of the receptor. The estrogen receptor also mediates gene transcription using different response elements (ie, AP-1) and other signal pathways. Recent advances in the molecular pharmacology of estrogen and estrogen receptors have resulted in the development of selective estrogen receptor modulators (eg, clomiphene, raloxifene, tamoxifen, toremifene), agents that bind and activate the estrogen receptor but that exhibit tissue-specific effects distinct from estrogen. Tissue-specific estrogen-agonist or -antagonist activity of these drugs appears to be related to structural differences in their estrogen receptor complex (eg, specifically the surface topography of AF-2 for raloxifene) compared with the estrogen (estradiol)-estrogen receptor complex. A second estrogen receptor also has been identified, and existence of at least 2 estrogen receptors (ER-alpha, ER-beta) may contribute to the tissue-specific activity of selective modulators. While the role of the estrogen receptor in bone, cardiovascular tissue, and the CNS continues to be studied, emerging evidence indicates that the mechanism of action of estrogen receptors in these tissues differs from the manner in which estrogen receptors function in reproductive tissue. /Estrogen General Statement/ Intracellular cytosol-binding proteins for estrogens have been identified in estrogen-responsive tissues including the female genital organs, breasts, pituitary, and hypothalamus. The estrogen-binding protein complex (ie, cytosol-binding protein and estrogen) distributes into the cell nucleus where it stimulates DNA, RNA, and protein synthesis. The presence of these receptor proteins is responsible for the palliative response to estrogen therapy in women with metastatic carcinoma of the breast. /Estrogen General Statement/ Estrogens have generally favorable effects on blood cholesterol and phospholipid concentrations. Estrogens reduce LDL-cholesterol and increase HDL-cholesterol concentrations in a dose-related manner. The decrease in LDL-cholesterol concentrations