Ovestin (Estriol)

Estriol acts on the estrogen pathway to relieve urogenital manifestations of menopause and to support hormone replacement regimens.

• Menopausal vulvovaginal atrophy: improves vaginal dryness, irritation and dyspareunia.
• Postmenopausal estrogen deficiency: alleviates mild urogenital discomfort and urinary symptoms.
• Adjunct in hormone replacement therapy: contributes to systemic estrogen balance in selected patients.

• Estriol binds to estrogen receptors (ERα and ERβ) in target tissues, especially the vaginal epithelium and lower urinary tract. Its weak estrogenic activity stimulates cellular proliferation, increases mucosal thickness, and enhances local blood flow, thereby restoring normal vaginal physiology and reducing atrophic changes.

Estriol may cause a range of adverse reactions, most of which are mild and reversible.

Common Side Effects

• Vaginal irritation or burning sensation
• Increased vaginal discharge or spotting
• Itching or mild rash at the application site
• Headache
• Breast tenderness
• Nausea

Serious or Rare Side Effects

• Endometrial hyperplasia or abnormal uterine bleeding
• Thromboembolic events (deep vein thrombosis, pulmonary embolism)
• Severe allergic reaction (anaphylaxis, angioedema)
• Uterine perforation (very rare)
• Severe skin rash or Stevens‑Johnson syndrome
• Hepatic dysfunction in susceptible individuals

Before initiating estriol therapy, clinicians should evaluate individual risk factors and contraindications.

• Assess estrogen status: confirm indication and baseline hormone levels.
• Avoid in estrogen‑dependent neoplasia: contraindicated in known breast or uterine cancer.
• Monitor for thromboembolic risk: use caution in patients with clotting disorders or a history of thrombosis.
• Consider liver function: adjust or avoid in severe hepatic impairment.
• Pregnancy and lactation: not recommended due to limited safety data.
• Store at ambient temperature: keep in the original container, protect from moisture and light.

Estriol can interact with several drug classes, altering efficacy or safety.

Major Interactions (Avoid)

• Combined oral contraceptives: increased estrogen load may raise clotting risk.
• Anticoagulants (e.g., warfarin): may potentiate bleeding tendencies.
• Selective estrogen receptor modulators (SERMs): antagonistic hormonal effects.

Moderate Interactions (Monitor Closely)

• Thyroid hormone replacement: estriol may affect thyroid‑binding globulin levels.
• Antihypertensives: possible fluid retention may modify blood pressure control.
• CYP450 inducers (e.g., rifampicin): may reduce estriol plasma concentrations.