Source: Health Products Regulatory Authority (ZA) Revision Year: 2022 Publisher: PHARMACARE LIMITED, Healthcare Park, Woodlands Drive, Woodmead 2191
Pharmacotherapeutic group: Progestogens
ATC code: G03D
Dienogest is a nortestosterone derivative with no androgenic activity. Dienogest binds to the progesterone receptor of the human uterus with only 10% of the relative affinity of progesterones. Despite its low affinity to the progesterone receptor, dienogest has a strong progestogenic effect in vivo. Dienogest has no significant androgenic, mineralocorticoid or glucocorticoid activity in vivo.
Dienogest acts on endometriosis by abolishing the trophic effects of oestradiol on both the eutopic and ectopic endometrium. When given continuously, dienogest leads to a hypoestrogenic, hypergestagenic endocrine environment and decidualisation of endometrial tissue.
Orally administered dienogest is almost completely absorbed.
Peak serum concentrations of 47 ng/ml are reached at about 1, 5 hours after ingestion of a 2 mg tablet. A standardised high fat meal did not affect the bioavailability of dienogest.
Bioavailability is about 91%. The pharmacokinetics of dienogest are dose-proportional within the dose range of 1 to 8 mg.
Dienogest is bound to serum albumin and does not bind to sex hormone binding globulin (SHBG) or corticoid binding globulin (CBG). 10% of the total serum concentration of the active medicine is present as free steroid, 90% is nonspecifically bound to albumin. The apparent volume of distribution (Vd/F) of dienogest is 40 litres.
Dienogest is completely metabolised by the known pathway of steroid metabolism, with the formation of inactive metabolites. Based on the in vivo and in vitro studies, CYP3A4 is the major enzyme involved in the metabolism of dienogest. The metabolites are rapidly excreted so that in plasma, unchanged dienogest is the dominating fraction.
The metabolic clearance rate from serum Cl/F is 64 ml/min.
Dienogest serum levels decrease in two phases. The terminal disposition phase is characterised by a half-life of approximately 9 to 10 hours.
Dienogest is excreted in the form of metabolites which are excreted at a urinary to faecal ratio of about 3:1 after oral administration of 0, 1 mg/kg. The half-life of urinary metabolites excretion is 14 hours. Following oral administration, approximately 86% of the dose administered is eliminated within 6 days; the bulk of this amount is excreted within the first 24 hours, mostly with the urine.
The pharmacokinetics of dienogest after repeated administration, can be predicted from single dose pharmacokinetics.
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