Estriol

Products

Estriol is commercially available in many countries as vaginal gel, vaginal cream, vaginal suppositories, vaginal tablets, and tablets for peroral therapy. This article refers to topical use.

Structure and properties

Estriol (C18H24O3, Mr = 288.4 g/mol) exists as a white crystalline powder that is practically insoluble in water. It is a natural metabolite of estradiol, which is most abundant in the bloodstream of women. Estriol is produced synthetically, but is identical to natural estrogen. The suffix -triol refers to the three hydroxyl groups.

Effects

Estriol (ATC GO3CA04) corrects estrogen deficiency, relieving the symptoms of vaginal atrophy. It normalizes the epithelium of the vagina, cervix, and urethra and has a beneficial effect on the microflora of the vagina. In therapeutic doses, estriol hardly causes proliferation of the endometrium. The duration of action is relatively short compared to other estrogens and the potency is weaker. The effects are due to binding to estrogen receptors.

Indications

Locally, estriol is used primarily for the treatment of vaginal atrophy due to estrogen deficiency in women, particularly after menopause. Orally, it is taken for the treatment of symptoms of estrogen deficiency due to natural or artificial menopause.

Dosage

According to the SmPC. Estriol is usually administered vaginally. Initially, it is applied once daily; for maintenance therapy, the dosing interval can also be extended (e.g., twice a week). However, tablets are also available for oral therapy.

Contraindications

Contraindications include (selection):

  • Hypersensitivity
  • Breast cancer, including patient history
  • Estrogen-dependent tumors, e.g., of the endometrium.
  • Endometriosis
  • Thromoboembolic events in patient history.
  • Acute or past liver disease
  • Pregnancy, lactation

Full precautions can be found in the drug label.

Interactions

Systemic interactions are considered unlikely with topical therapy. Interactions with CYP450 inducers cannot be excluded. The preparations may damage contraceptive devices such as condoms or diaphragms.

Adverse effects

The most common possible adverse effects include itching. Serious estrogen side effects, such as thromboembolic disease, are considered unlikely to occur with topical treatment because of the low dose.