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GENITO URINARY SYSTEM AND SEX HORMONES › SEX HORMONES AND MODULATORS OF THE GENITAL SYSTEM › ESTROGENS › Estrogens, combinations with other drugs
estriol
G03CC06
Forms & Strengths
- Vaginal cream: 0.01%, 0.1%
- Vaginal suppositories / pessaries: 0.5 mg
- Oral tablets: 1 mg, 2 mg
Adult Dosing
- Atrophic vaginitis / Vulvovaginal atrophy: 0.5 mg daily for 2-3 weeks, then tapered to a maintenance dose of 0.5 mg twice weekly
- Preoperative and postoperative care in postmenopausal women: 0.5 mg daily for 2 weeks prior to surgery; 0.5 mg twice weekly postoperatively
- Climacteric symptoms: 1-2 mg daily orally, adjusted according to response
Pediatric Dosing
- Not indicated for pediatric use
- Safety and efficacy in children and adolescents have not been established
Indications
- Treatment of estrogen deficiency associated with menopausal atrophic vaginitis and vulvovaginal atrophy
- Pre- and post-operative therapy in postmenopausal women undergoing vaginal surgery
- Management of climacteric symptoms (vasomotor symptoms, urogenital aging) where approved regionally
Mechanism of Action
- Short-acting estrogen receptor agonist with high binding affinity for nuclear estrogen receptors in vaginal, vulvar, and trigeminal tissues
- Promotes proliferation of the vaginal epithelium, restores normal vaginal pH, and enhances local urogenital blood flow
Contraindications
- Known, suspected, or history of breast cancer
- Known or suspected estrogen-dependent malignant tumors (e.g., endometrial cancer)
- Undiagnosed genital bleeding
- Active deep vein thrombosis, pulmonary embolism, or a history of these conditions
- Active or recent arterial thromboembolic disease (e.g., stroke, myocardial infarction)
- Liver dysfunction or disease where liver function tests have failed to return to normal
- Known hypersensitivity to estriol or any excipients
- Porphyria
Adverse Reactions
- Local irritation, pruritus, or burning at the application site (vaginal preparations)
- Increased vaginal discharge
- Breast tenderness or enlargement
- Breakthrough bleeding, spotting, or metrorrhagia
- Nausea and abdominal cramps
- Headache
Drug Interactions
- Metabolized by cytochrome P450 enzymes (primarily CYP3A4); inducers (e.g., rifampin, carbamazepine, St. John's wort) may decrease plasma concentrations
- Inhibitors of CYP3A4 (e.g., ketoconazole, erythromycin) may increase plasma concentrations
- May potentially alter the efficacy of antihypertensive agents and oral anticoagulants
- Systemic absorption from vaginal formulations is minimal, but concurrent use with other estrogens should be avoided to prevent cumulative estrogenic exposure
Curated Content: Needs Vetting Before Put to Clinical Use