Estriol is a naturally occurring, short-acting estrogen hormone, specifically an estrogen steroid. It is one of the three major endogenous estrogens, alongside estradiol and estrone. In the Indian therapeutic context, 1mg oral estriol is primarily used for the management of menopausal symptoms, particularly urogenital atrophy (vaginal dryness, dyspareunia, urinary urgency). It is considered a 'weaker' estrogen with a more favorable safety profile for vaginal and vulvar tissues, offering relief with potentially lower systemic absorption and reduced endometrial stimulation compared to estradiol.
Adult: For urogenital atrophy: 1mg to 2mg orally per day, usually given as a single dose or in divided doses. Treatment is often initiated daily and may be reduced to a maintenance dose (e.g., 0.5mg - 1mg daily) based on response. For systemic HRT, doses may be higher (2-4 mg/day), but estradiol is preferred.
Note: Take orally with or without food. Administer at the same time each day to maintain steady levels. For women with an intact uterus, a progestin must be added for at least 10-14 days per cycle to prevent endometrial hyperplasia. Therapy should be used at the lowest effective dose for the shortest duration consistent with treatment goals.
Estriol binds to and activates nuclear estrogen receptors (ERΞ± and ERΞ²) in target tissues. The receptor-hormone complex then binds to specific DNA sequences (Estrogen Response Elements - EREs), modulating gene transcription. This leads to cellular proliferation and differentiation in estrogen-responsive tissues like the vagina, vulva, urethra, and lower urinary tract.
Pregnancy: CONTRANDICATED. Estriol is a pregnancy category X drug. It is a natural estrogen present during pregnancy but exogenous administration can cause fetal harm, including congenital reproductive tract abnormalities. Not for use in pregnancy.
Driving: May cause dizziness or visual disturbances. Patients should be cautioned about driving or operating machinery until they know how the drug affects them.
| Enzyme Inducers (Carbamazepine, Phenytoin, Rifampicin, St. John's Wort) | Significantly increase estriol metabolism, reducing its therapeutic effect. | Major |
| Anticoagulants (Warfarin) | Estrogens may reduce anticoagulant effect; increased risk of thromboembolism. | Major |
| Cyclosporine | Estrogens may increase cyclosporine toxicity by inhibiting its metabolism. | Moderate |
| Thyroid Hormones (Levothyroxine) | Estrogens may increase thyroxine-binding globulin, potentially requiring dose adjustment of thyroid hormone. | Moderate |
| Corticosteroids | Estrogens may potentiate the anti-inflammatory effects and side effects of corticosteroids. | Moderate |
| Antidiabetic agents (Insulin, Sulfonylureas) | Estrogens may impair glucose tolerance, requiring adjustment of antidiabetic therapy. | Moderate |
Same composition (Estriol (1mg)), different brands: