Pharmacodynamics
Estriol binds to the estrogen receptor in the nucleus, thereby stimulating cells to produce proteins. Increased sex hormone-binding globulin and thyroid hormone-binding globulin are synthesized and follicle-stimulating hormone is suppressed. The proteins formed mediate the effect of estriol on the target cell. It also positively affects the microflora of the vagina and alleviates the discomfort of vaginal mucosal involution.
Pharmakokinetik
Estriol is rapidly and completely absorbed, with only 1-2% of the ingested dose entering the systemic circulation. Metabolism occurs in the liver and intestine. In plasma, it circulates at 91% protein-bound, with maximum plasma concentration reached after 5 hours. In relation to other estrogens, the effect lasts shorter and is weaker. Estriol is almost entirely excreted renally.
Contraindications
Estriol should not be used in case of:
- Hypersensitivity
- Breast cancer
- estrogen-dependent tumors
- Endometriosis
- Thromboembolic diseases
- severe renal failure
- Liver disease
- Pregnancy and lactation
Drug interactions
Estriol may interact with drugs that affect the CYP450 enzyme, resulting in either increased or decreased plasma estriol levels. Systemic interactions are unlikely when used topically.