Estriol

Estriol is a bioidentical estrogen hormone primarily indicated for the management of urogenital symptoms associated with menopause, such as vaginal dryness, atrophy, and related dyspareunia. As a weak estrogen, it offers a favorable safety profile for localized treatment, with minimal systemic absorption compared to stronger estrogens like estradiol. This product card provides a comprehensive, evidence-based overview for healthcare professionals considering its therapeutic application.

Features

• Active Ingredient: Estriol (oestriol)
• Common Formulations: Vaginal cream (0.1%, 0.5mg/g), vaginal tablets (0.03mg, 0.5mg), topical gel
• Bioidentical Structure: Molecularly identical to endogenous human estriol
• Low Systemic Absorption: Primarily acts locally on vaginal epithelium when administered topically
• Prescription Status: Available by prescription in most jurisdictions
• Half-Life: Approximately 6–9 hours

Benefits

• Effectively restores vaginal epithelial integrity and thickness
• Alleviates symptoms of genitourinary syndrome of menopause (GSM), including dryness, burning, and itching
• Reduces the incidence of urinary tract infections in postmenopausal women by improving urogenital flora and pH
• Improves vaginal lubrication and elasticity, enhancing comfort during intercourse
• Minimizes systemic estrogenic effects due to preferential local action
• May support overall urogenital health and quality of life in menopausal patients

Common use

Estriol is predominantly prescribed for the treatment of atrophic vaginitis and associated urogenital symptoms in postmenopausal individuals. It is also utilized off-label in compounded preparations for hormonal support in perimenopause, though robust clinical evidence for systemic use is limited. Its application is common in patients seeking to avoid the stronger systemic effects of estradiol or those with contraindications to conventional hormone replacement therapy (HRT). Topical estriol is particularly favored for patients with a history of hormone-sensitive cancers under specialist supervision, given its weak estrogenic potency.

Dosage and direction

Dosage varies by formulation and indication. For vaginal cream (0.1%): Initially, 2–4 grams intravaginally daily for 1–2 weeks, followed by a maintenance dose of 1 gram 1–3 times per week. For vaginal tablets (0.03mg): One tablet daily for two weeks, then twice weekly thereafter. Administration should be performed at bedtime to minimize leakage. Patients should be advised to use the applicator provided and wash it after each use. Treatment duration is individualized; periodic reevaluation of continued necessity is recommended, typically every 3–6 months.

Precautions

Patients should be screened for personal or family history of hormone-sensitive cancers, thromboembolic disorders, or cardiovascular disease prior to initiation. Although systemic absorption is low, caution is advised in patients with impaired liver function, as estrogens are metabolized hepatically. Regular gynecological examinations are recommended to monitor endometrial status, particularly in women with an intact uterus. Use with caution in patients with allergies to soy or peanuts, as some formulations may contain related excipients.

Contraindications

Estriol is contraindicated in individuals with known hypersensitivity to estriol or any component of the formulation. It should not be used in patients with undiagnosed abnormal genital bleeding, known or suspected estrogen-dependent neoplasia (e.g., breast or endometrial cancer), active deep vein thrombosis, pulmonary embolism, or active arterial thromboembolic disease. It is also contraindicated in patients with acute liver disease or a history of jaundice during prior estrogen use.

Possible side effect

Common local side effects may include vaginal irritation, itching, discharge, or spotting. Systemic effects are rare but may comprise breast tenderness, headache, nausea, or abdominal bloating. Very rarely, allergic reactions such as rash or urticaria may occur. Long-term use, even at low doses, may carry a theoretical risk of endometrial hyperplasia if unopposed in non-hysterectomized patients, though evidence is limited due to estriol’s weak estrogenic activity.

Drug interaction

Estriol may interact with drugs that induce hepatic enzymes (e.g., rifampicin, carbamazepine, St. John’s wort), potentially reducing its efficacy. Conversely, it may alter the metabolism of other hepatically cleared medications. It might also impact the efficacy of thyroid hormone replacement therapy by increasing sex hormone-binding globulin (SHBG). Concomitant use with other topical vaginal products (e.g., antifungal creams) should be spaced to avoid dilution or interaction.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next dose. In that case, the missed dose should be skipped, and the regular dosing schedule resumed. Doubling the dose is not recommended. For intermittent dosing regimens (e.g., twice weekly), patients may take the missed dose and adjust the schedule accordingly, maintaining at least a two-day interval between applications.

Overdose

Acute overdose with topical estriol is unlikely due to its formulation and route. However, excessive application could theoretically lead to systemic estrogenic effects such as nausea, vomiting, or breast tenderness. Treatment is supportive; gastric lavage is not indicated for topical formulations. Medical attention should be sought if significant systemic symptoms occur.

Storage

Store at room temperature (15–30°C), away from light and moisture. Do not freeze. Keep out of reach of children and pets. Discard any unused product after the expiration date printed on the packaging. For vaginal creams, avoid contamination of the tube tip by cleaning after each use.

Disclaimer

This information is intended for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting or altering any therapeutic regimen. Individual patient responses may vary. The prescriber is responsible for verifying dosage, indications, and contraindications based on the latest clinical guidelines and the patient’s health status.

Reviews

Clinical studies and meta-analyses generally support the efficacy and safety of topical estriol for vaginal atrophy. In a 2021 systematic review, estriol demonstrated significant improvement in vaginal health index scores and patient-reported symptoms compared to placebo. Patient satisfaction is often high due to minimal systemic side effects and rapid symptomatic relief. Some critics note the relative lack of large-scale, long-term data compared to estradiol-based therapies, but its niche in managing localized symptoms remains well-established in gynecological practice.