ELESTRIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ELESTRIN (ELESTRIN).
Estradiol is a hormone that binds to estrogen receptors (ERα and ERβ), activating transcription of estrogen-responsive genes, leading to effects such as endometrial growth, breast development, and regulation of the menstrual cycle. It also has non-genomic actions via membrane-associated estrogen receptors.
| Metabolism | Primarily hepatic via CYP3A4; undergoes enterohepatic recirculation. Metabolites include estrone and estriol, which are conjugated with sulfate or glucuronide and excreted in urine. |
| Excretion | Estradiol (active metabolite of estradiol hemihydrate) is primarily excreted in urine as glucuronide and sulfate conjugates (approximately 60-80%), with about 10% excreted in feces via bile. Unchanged estradiol excretion is minimal. |
| Half-life | Terminal elimination half-life of estradiol is approximately 13-16 hours. Steady-state concentrations are achieved after 2-4 days of daily application. Clinical context: The half-life supports once-daily dosing for transdermal delivery. |
| Protein binding | Estradiol is 97.5-99% bound to plasma proteins, primarily albumin (60-70%) and sex hormone-binding globulin (SHBG, 30-40%). |
| Volume of Distribution | Volume of distribution of estradiol is approximately 1.2 L/kg (range 0.9-1.5 L/kg). This high Vd indicates extensive tissue distribution and binding, including to estrogen receptors in target organs. |
| Bioavailability | Transdermal gel: Bioavailability is approximately 3-5% compared to intravenous administration due to skin metabolism and retention. The absolute bioavailability via the transdermal route is 82% relative to a reference transdermal delivery system. Oral estradiol has low bioavailability (5-10%) due to first-pass metabolism. |
| Onset of Action | Transdermal: Estradiol levels rise within 1-2 hours after application, with therapeutic levels achieved by 4 hours. Clinical effects on vasomotor symptoms (e.g., hot flashes) are typically observed after 2-4 weeks of daily use. |
| Duration of Action | Transdermal: Therapeutic effect persists over the 24-hour dosing interval with steady-state levels maintained for 24 hours. Removal of the gel leads to a decline in estradiol levels over 12-24 hours, but clinical effects may wane over several days due to continued receptor activation. |
Apply 1.25 g (2 actuations) of 0.06% gel to upper arm/shoulder once daily; may adjust based on response.
| Dosage form | GEL, METERED |
| Renal impairment | No specific dose adjustment provided; use with caution in severe renal impairment. |
| Liver impairment | Contraindicated in severe hepatic disease (Child-Pugh class C); use with caution in mild to moderate impairment. |
| Pediatric use | Not recommended for use in pediatric patients; safety and efficacy not established. |
| Geriatric use | Use with caution; consider lower starting dose due to increased risk of adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ELESTRIN (ELESTRIN).
| Breastfeeding | Estradiol is excreted in breast milk in small amounts. The milk-to-plasma ratio is estimated at 0.2-0.4. Limited data suggest no adverse effects in nursing infants at typical doses, but caution is advised due to potential for reduced milk production. Use only if clearly needed. |
| Teratogenic Risk | Estrogens are not recommended during pregnancy. First trimester: increased risk of congenital anomalies (e.g., cardiovascular defects, limb reduction). Second/third trimester: fetal harm including vaginal adenosis, cervical erosion, and possible transplacental carcinogenesis. Use is contraindicated in pregnancy. |
■ FDA Black Box Warning
Estrogens should not be used to prevent cardiovascular disease or dementia. Increased risks of endometrial cancer, breast cancer, stroke, and pulmonary embolism have been reported. Use with progestin in women with an intact uterus reduces risk of endometrial hyperplasia/carcinoma.
| Serious Effects |
["Undiagnosed abnormal genital bleeding","Known, suspected, or history of breast cancer","Known or suspected estrogen-dependent neoplasia (e.g., endometrial cancer)","Active DVT, PE, or history of these conditions","Active or recent arterial thromboembolic disease (e.g., stroke, MI)","Known protein C, protein S, or antithrombin deficiency or other thrombophilic disorders","Hepatic impairment or disease","Known or suspected pregnancy","Hypersensitivity to estradiol or any component of the product"]
| Precautions | ["Risk of endometrial cancer: Use adequate progestin in women with an intact uterus","Cardiovascular disorders: Increased risk of stroke, DVT, pulmonary embolism, MI, especially in smokers and women with hypertension","Breast cancer: Increased risk with prolonged use, especially with combination therapy","Dementia: Increased risk in women over 65","Gallbladder disease: Increased risk","Hypertriglyceridemia: May occur, caution in patients with elevated triglycerides","Hepatic impairment: Use caution, monitor liver function","Hypothyroidism: May increase thyroid-binding globulin, adjust thyroid replacement","Fluid retention: Use caution in conditions affected by edema","Hypocalcemia: Use caution in patients with hypoparathyroidism","Ovarian cancer: Possibly increased risk with estrogen-alone use","Exacerbation of endometriosis","Hereditary angioedema: May exacerbate","Porphyria: May exacerbate"] |
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| Fetal Monitoring | Monitor maternal blood pressure, signs of thromboembolism, and liver function. In pregnancy, perform fetal ultrasound for anatomy and growth if inadvertent exposure. No standard fetal monitoring required when used in non-pregnant women. |
| Fertility Effects | Estradiol may suppress ovulation; thus, it can impair fertility when used as contraception. Reversible upon discontinuation. |
| Food/Dietary | Grapefruit and grapefruit juice may increase estradiol systemic exposure and should be avoided during treatment. No other significant food interactions are known. |
| Clinical Pearls | ELESTRIN (estradiol vaginal gel) is a bioidentical estradiol formulation for moderate-to-severe dyspareunia due to vulvar and vaginal atrophy. Apply exactly at the applicator mark; overapplication does not increase efficacy but raises systemic absorption. Use the lowest effective dose for the shortest duration. Contraindicated in undiagnosed vaginal bleeding, breast cancer (known/suspected), or estrogen-dependent neoplasia. |
| Patient Advice | Apply the gel at the same time each day, using the provided applicator to the exact fill line. · Do not use more than prescribed; more gel does not improve symptoms and increases systemic estrogen exposure. · Wash hands immediately after application; avoid contact with others (especially men, children, pets) until the gel dries. · Report any unexpected vaginal bleeding, breast lumps, or signs of thromboembolism (chest pain, leg swelling, sudden headache) to your healthcare provider. · If you are a smoker over 35, you have an increased risk of serious cardiovascular side effects; discuss smoking cessation with your doctor. · Do not use vaginal lubricants or other products within 30 minutes before or after applying ELESTRIN, as they may interfere with absorption. |