IMVEXXY
Clinical safety rating: caution
Comprehensive clinical and safety monograph for IMVEXXY (IMVEXXY).
Estradiol, a form of estrogen, binds to estrogen receptors (ERα and ERβ) in target tissues, modulating gene transcription and producing effects such as proliferation of the vaginal epithelium and increased cervical secretions, which relieve vulvar and vaginal atrophy symptoms.
| Metabolism | Estradiol is primarily metabolized in the liver via conversion to estrone and estriol, which are further metabolized via hydroxylation, glucuronidation, and sulfation. Key enzymes include CYP450 isoforms (e.g., CYP1A2, CYP3A4) and UDP-glucuronosyltransferases (UGTs). |
| Excretion | Primarily renal as glucuronide conjugates; approximately 30-50% of a dose is excreted in urine as estradiol metabolites, with ~10% excreted in feces via biliary elimination. |
| Half-life | Terminal elimination half-life of estradiol is approximately 13-14 hours (range 10-16 hours) after vaginal administration, supporting once-daily dosing. |
| Protein binding | Estradiol is approximately 98% bound to serum proteins, mainly sex hormone-binding globulin (SHBG, ~40%) and albumin (~58%). |
| Volume of Distribution | Apparent volume of distribution of estradiol is approximately 1.7 L/kg, indicating extensive distribution into tissues. |
| Bioavailability | Bioavailability after vaginal administration is approximately 5-10% relative to oral administration due to first-pass hepatic metabolism; peak concentrations are lower than oral but more consistent. |
| Onset of Action | Systemic estradiol levels peak within 1-4 hours after vaginal administration; clinical effect on vasomotor symptoms may be noted within 2-4 weeks. |
| Duration of Action | Duration of action for systemic effects is approximately 24 hours with daily dosing; for local effects (vaginal atrophy), therapeutic benefit persists with continued use. |
IMVEXXY (estradiol vaginal insert) 10 mcg inserted vaginally once daily for 2 weeks, then twice weekly (e.g., Monday and Thursday).
| Dosage form | INSERT |
| Renal impairment | No dose adjustment required for renal impairment; pharmacokinetics not studied in severe renal impairment. |
| Liver impairment | Contraindicated in hepatic impairment; no specific Child-Pugh based guidelines available. |
| Pediatric use | Not indicated for pediatric patients; safety and efficacy not established. |
| Geriatric use | No specific dose adjustment; use lowest effective dose for shortest duration due to increased risk of thromboembolism and malignancy. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for IMVEXXY (IMVEXXY).
| Breastfeeding | Estradiol is present in human breast milk. The amount of estradiol transferred into breast milk after vaginal administration of IMVEXXY is expected to be low due to the low systemic absorption. The milk-to-plasma ratio (M/P ratio) for estradiol is not specifically reported for IMVEXXY, but for systemic estradiol, the M/P ratio is approximately 0.2-0.4. Because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother. |
| Teratogenic Risk | Estrogens are not recommended for use during pregnancy. IMVEXXY (estradiol vaginal insert) is indicated for the treatment of moderate to severe dyspareunia due to menopause and has no approved use in pregnancy. Data from epidemiologic studies and meta-analyses have not found an increased risk of major birth defects after first-trimester exposure to estrogens. However, prolonged exposure to estrogens during pregnancy has been associated with an increased risk of vaginal adenosis, cervical and vaginal clear cell adenocarcinoma in female offspring, and genital tract abnormalities in male offspring. Therefore, use is contraindicated in pregnancy. |
■ FDA Black Box Warning
Estrogen-Alone Therapy: Endometrial cancer – The risk of endometrial cancer is increased in women with a uterus using unopposed estrogens. Add a progestin if the uterus is intact. Cardiovascular disorders and probable dementia – Estrogen-alone therapy should not be used for the prevention of cardiovascular disease or dementia. The Women's Health Initiative (WHI) estrogen-alone substudy reported increased risks of stroke and deep vein thrombosis, and the WHI Memory Study reported an increased risk of probable dementia in women 65 years of age or older.
| Serious Effects |
["Known or suspected pregnancy","Undiagnosed abnormal genital bleeding","Known, suspected, or history of breast cancer","Known or suspected estrogen-dependent neoplasia","Active or history of venous thromboembolism (e.g., DVT, PE)","Active or history of arterial thromboembolism (e.g., stroke, MI)","Known protein C, protein S, or antithrombin deficiency, or other thrombophilic disorders","Hepatic impairment or disease","Known hypersensitivity to estradiol or any ingredients of IMVEXXY"]
| Precautions | ["Cardiovascular disorders (e.g., stroke, DVT)","Malignant neoplasms (e.g., endometrial cancer, breast cancer)","Gallbladder disease","Hypercalcemia","Visual abnormalities","Hepatic impairment","Fluid retention","Hypothyroidism","Hypertriglyceridemia","Exacerbation of endometriosis","Hereditary angioedema","Porphyria"] |
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| Fetal Monitoring | No specific maternal-fetal monitoring is required for IMVEXXY because it is not indicated for use in pregnancy. However, if inadvertent exposure occurs during pregnancy, no specific monitoring is recommended beyond routine prenatal care. |
| Fertility Effects | IMVEXXY is indicated for postmenopausal women and does not affect fertility. In premenopausal women, estradiol can affect fertility by interfering with ovulation via negative feedback on gonadotropin secretion. |