Myfembree

Uses

Treatment of moderate to severe vasomotor symptoms associated with the menopause.

Treatment of moderate to severe symptoms of vulvar and vaginal atrophy associated with the menopause. When prescribing solely for the treatment of symptoms of vulvar and vaginal atrophy, topical vaginal products should be considered.

Treatment of hypoestrogenism due to hypogonadism, castration or primary ovarian failure.

Treatment of breast cancer (for palliation only) in appropriately selected women and men with metastatic disease.

Treatment of advanced androgen-dependent carcinoma of the prostate (for palliation only).

Prevention of osteoporosis. When prescribing solely for the prevention of postmenopausal osteoporosis, therapy should only be considered for women at significant risk of osteoporosis and for whom non-estrogen medications are not considered to be appropriate.

Relugolix is an oral GnRH receptor antagonist for androgen deprivation therapy in the treatment of advanced prostate cancer.

Relugolix is indicated for the treatment of adult patients with advanced prostate cancer. In a combination product with estradiol and norethindrone, relugolix is indicated for the once-daily treatment for the management of heavy menstrual bleeding associated with uterine fibroids in premenopausal women.

Myfembree is also used to associated treatment for these conditions: Atrophic Vaginitis, Breast Cancer, Breast engorgement caused by Postpartum state, Hypogonadism female, Kraurosis Vulvae, Metastatic Breast Cancer, Osteoporosis, Postmenopausal Osteoporosis, Premature Ovarian Failure (POF), Prostate Cancer, Urogenital atrophy, Vasomotor Symptoms Associated With Menopause, Vulvovaginal Atrophy, Advanced androgen dependent Prostate cancer, Female castration, Hypoestrogenism, Contraception, Hormone Replacement Therapy, PalliationAdvanced Prostate Cancer, Heavy Menstrual Bleeding

How Myfembree works

Estrogen is found in the the breast, uterine, ovarian, skin, prostate, bone, fat, and brain tissues. The main source of estrogen in adult women during the reproductive period of life is the ovarian follicle, which secretes 70 to 500 mcg of estradiol each day. After menopause, however, the majority of endogenous estrogen is produced by transformation of androstenedione (which is secreted by the adrenal cortex) to estrone in the peripheral tissues. Both estrone and its sulphate conjugated form, estrone sulphate, represent the most abundant estrogens found in postmenopausal women.

Estradiol, however, is considerably more potent than estrone and estriol at the estrogen receptor (ER). As a result, the higher estrone concentration in postmenopausal population, can cause various undesirable effects. These effects may include hot flashes, chills, vaginal dryness, mood swings, irregular menstruation, and chills, in addition to sleep problems.

Estradiol workings by binding to subtypes of the estrogen receptor: estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). It also exerts potent agonism of G Protein-coupled estrogen receptor (GPER), which is recognized an important regulator of this drug's rapid effects. Once the estrogen receptor has bound to its ligand, it enters the nucleus of the target cell, regulating gene transcription and formation of of messenger RNA. This mRNA makes contact with ribosomes producing specific proteins that express the effect of estradiol upon the target cell. Agonism of estrogen receptors increases pro-estrogenic effects, leading to the relief of vasomotor and urogenital symptoms of a postmenopausal or low estradiol state.

The pathogenesis and progression of prostate cancer appear driven, at least in part, by the effects of testosterone. Androgen deprivation has been demonstrated to result in cell death and tumor regression in many well-differentiated prostate cancer cell lines - for this reason, androgen deprivation therapy (ADT) has become a standard in the treatment of prostate cancer, particularly in advanced disease.

Testosterone production in males is carried out in the Leydig cells of testes and is stimulated by luteinizing hormone (LH), which itself is produced in the pituitary gland following the binding of gonadotropin-releasing hormone (GnRH) to corresponding GnRH receptors. Relugolix is a competitive antagonist of these GnRH receptors, thereby decreasing the release of LH and, ultimately, testosterone.

Dosage

Myfembree dosage

Oral:

• Prostate cancer: 10 mg 3 times/day for at least 3 month.
• Menopausal vasomotor symptoms: 1-2 mg/day on a cyclical or continuous regimen
• Prevention of postmenopausal osteoporosis: 0.5 mg/day in cyclical regimen.
• Hypogonadism: 1-2 mg/day in a cyclic regimen.

Vaginal:

• Vulvular and vag atrophy: Insert 2-4 g/day for 2 wk. Maintenance: 1 g 1-3 times/wk.
• Postmenopausal vag atrophy; Urogenital symptoms: Insert a ring and keep in place for 90 days.
• Atrophic vaginitis: Insert 1 tab once daily for 2 wk. Maintenance: 1 tab twice wkly. Attempt to discontinue or taper medication at 3-6 monthly intervals.

Side Effects

GI disturbances, genitourinary changes, haematologic disorders, CV and CNS effects, endocrine and metabolic disorders, cholestatic jaundice, local skin reactions, chorea, contact lens intolerance, steeping of corneal curvature, pulmonary thromboembolism, carbohydrate intolerance.

Toxicity

The NOAEL (no-observed-adverse-effect-level) oral toxicity of estradiol after 90 day in rats was 0.003 mg/kg/day for blood, female reproductive, and male reproductive, endocrine, and liver toxicity. Oral TDLO of ethinyl estradiol is 21 mg/kg/21D intermittent, woman) with an oral LD50 of 960 mg/kg in the rat.

There is limited information in the literature regarding estrogen overdose. Estradiol overdose likely leads to the occurrence of estrogen-associated adverse effects, including nausea, vomiting, abdominal pain, breast tenderness, venous thrombosis, and vaginal bleeding. It is generally recommend to discontinue estradiol treatment and offer supportive care in the case of an overdose.

Data regarding overdose of relugolix are unavailable.

Precaution

Conditions exacerbated by fluid retention; hypercalcaemia, cerebrovascular diorders, coronary artery disease, gall bladder diseases; lipid effects; familial defects of lipoprotein metabolism. May increase BP, risk of venous thromboembolism, breast cancer, benign hepatic adenoma, endometrial cancer and size of preexisting uterine leiomyomata. Dosage should be reduced in hepatic impairment. Lactation. Child.

Interaction

CYP1A2 and CYP3A4 inducers e.g. aminoglutethimide, carbamazepine, phenobarbital, and rifampin may decrease the effects of estradiol. May enhance the effects of hydrocortisone and prednisolone when used together.

Volume of Distribution

Estrogens administered exogenously distribute in a similar fashion to endogenous estrogens. They can be found throughout the body, especially in the sex hormone target organs, such as the breast, ovaries and uterus.

Elimination Route

The absorption of several formulations of estradiol is described below:

Oral tablets and injections

First-pass metabolism in the gastrointestinal tract rapidly breaks down estradiol tablets before entering the systemic circulation. The bioavailability of oral estrogens is said to be 2-10% due to significant first-pass effects. The esterification of estradiol improves the administration (such as with estradiol valerate) or to sustain release from intramuscular depot injections (including estradiol cypionate) via higher lipophilicity. After absorption, the esters are cleaved, which leads to the release of endogenous estradiol, or 17β-estradiol.

Transdermal preparations

The transdermal preparations slowly release estradiol through intact skin, which sustains circulating levels of estradiol during a 1 week period of time. Notably, the bioavailability of estradiol after transdermal administration is about 20 times higher than after oral administration. Transdermal estradiol avoids first pass metabolism effects that reduce bioavailability. Administration via the buttock leads to a Cmax of about 174 pg/mL compared to 147 pg/mL via the abdomen.

Spray preparations

After daily administration, the spray formulations of estradiol reach steady state within 7-8 days. After 3 sprays daily, Cmax is about 54 pg/mL with a Tmax of 20 hours. AUC is about 471 pg•hr/mL.

Vaginal ring and cream preparations

Estradiol is efficiently absorbed through the mucous membranes of the vagina. The vaginal administration of estrogens evades first-pass metabolism. Tmax after vaginal ring delivery ranges from 0.5 to 1 hour. Cmax is about 63 pg/mL. The vaginal cream preparation has a Cmax of estradiol (a component of Premarin vaginal estrogen conjugate cream) was a Cmax of 12.8 ± 16.6 pg/mL, Tmax of 8.5 ± 6.2 hours, with an AUC of 231 ± 285 pg•hr/mL.

The C_max and AUC of orally-administered relugolix increase proportionally following single doses - in contrast, with repeat dosing the AUC remains proportional to the dose while the C_max increases greater than proportionally to the dose. Following the administration of 120mg once daily, the steady-state AUC and C_max of relugolix were 407 (± 168) ng.hr/mL and 70 (± 65) ng/mL, respectively.

The absolute oral bioavailability of relugolix is approximately 12% and the median T_max following oral administration is 2.25 hours.

Half Life

The terminal half-lives for various estrogen products post oral or intravenous administration has been reported to range from 1-12 hours. One pharmacokinetic study of oral estradiol valerate administration in postmenopausal women revealed a terminal elimination half-life of 16.9 ± 6.0 h. A pharmacokinetic study of intravenous estradiol administration in postmenopausal women showed an elimination half-life of 27.45 ± 5.65 minutes. The half-life of estradiol appears to vary by route of administration.

The average effective half-life of relugolix is 25 hours, while the average terminal elimination half-life is 60.8 hours.

Clearance

In one pharmacokinetic study, the clearance of orally administered micronized estradiol in postmenopausal women was 29.9±15.5 mL/min/kg. Another study revealed a clearance of intravenously administered estradiol was 1.3 mL/min/kg.

The average renal clearance of relugolix is 8 L/h with a total clearance of 26.4 L/h.

Elimination Route

Estradiol is excreted in the urine with both glucuronide and sulfate conjugates.

Approximately 81% of an orally administered dose was recovered in the feces, of which 4.2% was unchanged parent drug, while 4.1% of the dose was recovered in the urine, of which 2.2% remained unchanged.

Pregnancy & Breastfeeding use

Pregnancy Category X. Studies in animals or human beings have demonstrated foetal abnormalities or there is evidence of foetal risk based on human experience or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.

Contraindication

Hypersensitivity; undiagnosed vag bleeding; thrombophloebitis or thromboembolic disorders; breast carcinoma except in selected patients being treated for metastatic disease; oestrogen-dependent tumor; porphyria; pregnancy.

Storage Condition

Store at room temperature.

Innovators Monograph

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