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Pharmacotherapeutic group: Natural and semisynthetic estrogens, plain. ATC code: G03CA03.
Pharmacology: Pharmacodynamics: The active ingredient, synthetic 17β-estradiol, is chemically and biologically identical to endogenous human estradiol. It substitutes for the loss of oestrogen production in menopausal women, and alleviates menopausal symptoms.
Relief of menopausal symptoms is achieved during the first few weeks of treatment.
Pharmacokinetics: Novo Nordisk's orally administered micronised 17β-estradiol as contained in Estrofem is rapidly and efficiently absorbed from the gastrointestinal tract, reaching a peak plasma concentration of approximately 44 pg/ml (range 30-53 pg/ml) within 4-6 hours after intake of 2 mg. 17β-estradiol has a half life of approximately 14-16 hours. More than 90% of 17β-estradiol is bound to plasma proteins.
17β-estradiol is oxidised to estrone, which in turn is converted to estrone sulphate. Both transformations take place mainly in the liver. Oestrogens are excreted into the bile and then undergo reabsorption from the intestine. During this enterohepatic circulation, degradation occurs. 17β-estradiol and its metabolites are excreted in the urine (90-95%) as biologically inactive glucuronide and sulphate conjugates or in the faeces (5-10%) mostly unconjugated.
Toxicology: Preclinical safety data: Acute toxicity of oestrogens is low. Because of marked differences between animal species and between animals and humans preclinical results possess a limited predictive value for the application of oestrogens in humans.
In experimental animals estradiol or estradiol valerate displayed an embryolethal effect already at relatively low doses; malformations of the urogenital tract and feminisation of male fetuses were observed.
Preclinical data based on conventional studies of repeated dose toxicity, genotoxicity and carcinogenic potential revealed no particular human risks beyond those discussed in other sections of the monograph.
