MENOSTAR

Clinical safety rating: caution

Comprehensive clinical and safety monograph for MENOSTAR (MENOSTAR).

How it works

Estrogen receptor agonist; binds to estrogen receptors, leading to gene transcription and physiological effects.

What the body does with it

Metabolism	Hepatic via CYP3A4; undergoes enterohepatic recirculation.
Excretion	Renal (primarily as glucuronide and sulfate conjugates), ~40-60% of a dose excreted in urine; fecal excretion accounts for approximately 10-20% as unabsorbed drug or metabolites.
Half-life	Terminal half-life of estradiol is approximately 12-14 hours; with MENOSTAR (estradiol vaginal ring), systemic absorption is minimal, and the effective half-life for local effects is extended by continuous release over 90 days.
Protein binding	Estradiol is approximately 98% bound to sex hormone-binding globulin (SHBG) and albumin.
Volume of Distribution	Apparent Vd of estradiol is approximately 1.2 L/kg; this large volume reflects extensive distribution into tissues, but for MENOSTAR, systemic distribution is limited due to low absorption.
Bioavailability	Vaginal route: minimal systemic bioavailability (<10% of the dose absorbed systemically due to first-pass hepatic metabolism and local action).
Onset of Action	Vaginal administration: Clinically detectable effect on urogenital epithelium within 2-4 weeks of continuous use.
Duration of Action	Continuous local effect for the entire 90-day period of ring placement; systemic effects are minimal due to low absorption.

Classification & Brands

Dosing & administration

One Menostar (estradiol 14 mcg/day) transdermal system applied to the lower abdomen once weekly (every 7 days).

Dosage form	FILM, EXTENDED RELEASE
Renal impairment	No dosage adjustment required for renal impairment; estradiol pharmacokinetics not significantly altered in renal disease.
Liver impairment	Contraindicated in patients with impaired liver function or active liver disease; no adjustment guidelines available for Child-Pugh classes.
Pediatric use	Not indicated for use in pediatric patients; safety and efficacy not established.
Geriatric use	No specific dosage adjustment recommended; however, use the lowest effective dose for the shortest duration due to increased risk of thromboembolic events and malignancy in elderly women.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for MENOSTAR (MENOSTAR).

Breastfeeding	Excreted in breast milk in small amounts; M/P ratio not reported for conjugated estrogens; may interfere with lactation; not recommended in breastfeeding women; consider alternative therapy.
Teratogenic Risk	First trimester: Use contraindicated due to risk of urogenital tract abnormalities and cardiovascular defects; second and third trimester: Estrogen exposure associated with increased risk of endometrial adenocarcinoma and other malignancies in female offspring; no adequate studies; use only if clearly needed.

Warnings & precautions

■ FDA Black Box Warning

Estrogens increase the risk of endometrial cancer. Unopposed estrogen use increases risk of endometrial hyperplasia and carcinoma. Concomitant progestin therapy is recommended.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Undiagnosed abnormal genital bleeding","Known or suspected breast cancer (except for appropriately selected patients)","Known or suspected estrogen-dependent neoplasia","Active DVT, PE, or history of these conditions","Active arterial thromboembolic disease or history of these conditions (e.g., stroke, MI)","Known anaphylactic reaction or angioedema to estrogens","Hepatic impairment or disease","Known or suspected pregnancy"]

Clinical Precautions

Precautions

["Endometrial hyperplasia and carcinoma","Cardiovascular disorders (e.g., stroke, DVT, PE)","Breast cancer risk","Gallbladder disease","Hypertriglyceridemia","Fluid retention","Hereditary angioedema"]

Clinical Tips & Counseling

Drug interactions

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MENOSTAR

Clinical safety rating: caution

Comprehensive clinical and safety monograph for MENOSTAR (MENOSTAR).

How it works

Estrogen receptor agonist; binds to estrogen receptors, leading to gene transcription and physiological effects.

What the body does with it

Metabolism	Hepatic via CYP3A4; undergoes enterohepatic recirculation.
Excretion	Renal (primarily as glucuronide and sulfate conjugates), ~40-60% of a dose excreted in urine; fecal excretion accounts for approximately 10-20% as unabsorbed drug or metabolites.
Half-life	Terminal half-life of estradiol is approximately 12-14 hours; with MENOSTAR (estradiol vaginal ring), systemic absorption is minimal, and the effective half-life for local effects is extended by continuous release over 90 days.
Protein binding	Estradiol is approximately 98% bound to sex hormone-binding globulin (SHBG) and albumin.
Volume of Distribution	Apparent Vd of estradiol is approximately 1.2 L/kg; this large volume reflects extensive distribution into tissues, but for MENOSTAR, systemic distribution is limited due to low absorption.
Bioavailability	Vaginal route: minimal systemic bioavailability (<10% of the dose absorbed systemically due to first-pass hepatic metabolism and local action).
Onset of Action	Vaginal administration: Clinically detectable effect on urogenital epithelium within 2-4 weeks of continuous use.
Duration of Action	Continuous local effect for the entire 90-day period of ring placement; systemic effects are minimal due to low absorption.

Classification & Brands

Dosing & administration

One Menostar (estradiol 14 mcg/day) transdermal system applied to the lower abdomen once weekly (every 7 days).

Dosage form	FILM, EXTENDED RELEASE
Renal impairment	No dosage adjustment required for renal impairment; estradiol pharmacokinetics not significantly altered in renal disease.
Liver impairment	Contraindicated in patients with impaired liver function or active liver disease; no adjustment guidelines available for Child-Pugh classes.
Pediatric use	Not indicated for use in pediatric patients; safety and efficacy not established.
Geriatric use	No specific dosage adjustment recommended; however, use the lowest effective dose for the shortest duration due to increased risk of thromboembolic events and malignancy in elderly women.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for MENOSTAR (MENOSTAR).

Breastfeeding	Excreted in breast milk in small amounts; M/P ratio not reported for conjugated estrogens; may interfere with lactation; not recommended in breastfeeding women; consider alternative therapy.
Teratogenic Risk	First trimester: Use contraindicated due to risk of urogenital tract abnormalities and cardiovascular defects; second and third trimester: Estrogen exposure associated with increased risk of endometrial adenocarcinoma and other malignancies in female offspring; no adequate studies; use only if clearly needed.

Warnings & precautions

■ FDA Black Box Warning

Estrogens increase the risk of endometrial cancer. Unopposed estrogen use increases risk of endometrial hyperplasia and carcinoma. Concomitant progestin therapy is recommended.