Heragest Mechanism of Action

Pharmacologic Category: Progestogens. ATC Code: G03DA.
Pharmacology: Pharmacodynamics: Progesterone is a hormone produced in the ovaries (specifically the corpus luteum), the adrenal glands and in the placenta during pregnancy. It acts on the endometrium by converting the proliferating phase to the secretory phase. Progesterone is capable of inducing a normal full secretory endometrium and in particular, gestagenic, antiestrogenic, slightly antiandrogenic, and antialdosterone effects.
Pharmacokinetics: Micronized progesterone is absorbed in the gastrointestinal tract. After oral administration of 2 capsules (each capsule contains 200 mg progesterone) of progesterone in healthy volunteers, an increase in plasma progesterone levels to a maximum concentration of 13.8 ng/mL ± 2.9 ng/mL in 2.2 ± 1.4 hours was observed. The elimination half-life observed was 16.8 ± 2.3 hours.
Although there were inter-individual variations, the individual pharmacokinetic characteristics were maintained over several months, indicating predictable responses to the drug.
Approximately 96 to 99% of progesterone is bound to serum proteins, primarily to serum albumin (50 to 54%) and transcortin (43 to 48%).
Progesterone is metabolized primarily by the liver. The main plasma metabolites are 20α hydroxyl-△ 4α-prenolone and 5α-dihydrogesterone. Some progesterone metabolites are excreted in the bile and these may be conjugated and further metabolized in the gut via reduction, dehydroxylation and epimerization. The main plasma and urinary metabolites are similar to those found during the physiological secretion of the corpus luteum.
Progesterone is eliminated in the urine (95%) in the form of glycuroconjugated metabolites, mainly 3α, 5β-pregnanediol (pregnandiol).
Vaginal: First-pass metabolism in the gastrointestinal tract and liver is bypassed when progesterone is administered vaginally. After administration, plasma progesterone levels reach maximal concentrations within 3 to 8 hours, depending on the formulation used and gradually fall during the next 8 hours.