Pharmacotherapeutic group: Progestogens. ATC code: G03DB08.
Pharmacology: Pharmacodynamics: Dienogest is a nortestosterone derivative with no androgenic but rather an antiandrogenic activity of approximately one third of that of cyproterone acetate. Dienogest binds to the progesterone receptor of the human uterus with only 10% of the relative affinity of progesterone. 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 reducing the endogenous production of oestradiol and thereby suppresses the trophic effects of estradiol on both the eutopic and ectopic endometrium. When given continuously, dienogest leads to a hypoestrogenic, hypergestagenic endocrine environment causing initial decidualization of endometrial tissue followed by atrophy of endometriotic lesions.
Data on efficacy: Superiority of dienogest over placebo was demonstrated in a 3-months study including 198 patients with endometriosis. Endometriosis-associated pelvic pain was measured on a Visual Analog Scale (0-100 mm). After 3 months of treatment with Dienogest 2 mg a statistically significant difference compared to placebo (Δ = 12.3 mm; 95%CI: 6.4 - 18.1; p<0.0001) and a clinically meaningful reduction of pain compared to baseline (mean reduction = 27.4 mm ± 22.9) were demonstrated.
After 3 months of treatment, reduction of endometriosis-associated pelvic pain by 50% or more without relevant increase of concomitant pain medication was achieved in 32.4% of patients on Dienogest 2 mg (placebo: 13.5%); a reduction of endometriosis-associated pelvic pain by 75% or more without relevant increase of concomitant pain medication was achieved in 18.6% of patients on Dienogest 2mg (placebo: 5.2%).
The open-label extension to this placebo-controlled study suggested a continued improvement of endometriosis-associated pelvic pain for a treatment duration of up to 15 months.
The placebo controlled results were supported by the results obtained in a 6 months active-controlled study versus a GnRH agonist including 252 patients with endometriosis.
Three studies including a total of 252 patients who received a daily dose of 2 mg dienogest demonstrated a substantial reduction of endometriotic lesions after 6 months of treatment.
Data on safety: Endogenous estrogen levels are moderately suppressed during treatment with Dienogest 2 mg.
Currently, long-term data on bone mineral density (BMD) and risk of fractures in users of Dienogest 2 mg are not available.
No significant changes of the mean values of standard laboratory parameters (including haematology, blood chemistry, liver enzymes, lipids and HbA1C) were observed during treatment with Dienogest 2 mg.
Safety in adolescents: The safety of dienogest with respect to BMD was investigated in an uncontrolled clinical trial over 12 months in 111 adolescent women with clinically suspected or confirmed endometriosis. The mean relative change in BMD of the lumbar spine from baseline was -1.2%. In a subset of the patients with decreased BMD a follow-up measurement was performed 6 months after end of treatment and showed an increase in BMD towards pretreatment levels.
Pharmacokinetics: Absorption: Orally administered dienogest is rapidly and almost completely absorbed. Peak serum concentrations of 47 ng/ml are reached at about 1.5 hours after single ingestion. Bioavailability is about 91%. The pharmacokinetics of dienogest are dose-proportional within the dose range of 1 - 8 mg.
Distribution: 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 drug concentration is present as free steroid, 90% is non-specifically bound to albumin.
The apparent volume of distribution (Vd/F) of dienogest is 40 l.
Metabolism: Dienogest is completely metabolized by the known pathways of steroid metabolism, with the formation of endocrinologically mostly inactive metabolites. Based on in vitro and in vivo studies, CYP3A4 is the major enzyme involved in the metabolism of dienogest. The metabolites are excreted very quickly so that in plasma unchanged dienogest is the dominating fraction.
The metabolic clearance rate from serum Cl/F is 64 ml/min.
Elimination: Dienogest serum levels decrease in two phases. The terminal disposition phase is characterized by a half-life of approximately 9-10 hours. Dienogest is excreted in 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 excreted within the first 24 h, mostly with the urine.
Steady-state conditions: Pharmacokinetics of dienogest are not influenced by SHBG levels. Following daily ingestion drug serum levels increase about 1.24 fold reaching steady-state conditions after 4 days of treatment. The pharmacokinetics of dienogest after repeated administration of ENDOVELLE can be predicted from single dose pharmacokinetics.
Pharmacokinetics in Special Population: ENDOVELLE has not been studied specifically in renally impaired subjects.
ENDOVELLE has not been studied in subjects with hepatic impairment.
Toxicology: Preclinical safety data: Preclinical data reveal no special risks for humans based on conventional studies of repeated dose toxicity, genotoxicity, carcinogenic potential and toxicity to reproduction. However, it should be borne in mind that sex steroids can promote the growth of certain hormone-dependent tissues and tumours.