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Pharmacotherapeutic group: Sex hormones and modulators of the genital system, progestogens and oestrogens, fixed combinations. ATC code: G03AA18.
PHARMACOLOGY: Pharmacodynamics: Mechanism of action: Nextstellis contains the oestrogen estetrol and the progestogen drospirenone. Estetrol is an oestrogen that is only produced during pregnancy by the human foetal liver.
Estetrol demonstrates anti-gonadotropic activity characterised by a dose-dependent decrease in both serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels.
The progestogen drospirenone possesses progestagenic, antigonadotropic, antiandrogenic and mild antimineralocorticoid properties and has no oestrogenic, glucocorticoid or antiglucocorticoid activity. These properties are pharmacologically similar to the natural hormone progesterone.
The contraceptive effect of Nextstellis is based on the interaction of various factors, the most important of which is inhibition of ovulation.
Clinical efficacy and safety: Two clinical studies were performed worldwide, one pivotal study in the EU/Russia and a supportive study in the US in women between 16 and 50 years of age for 13 cycles/1 year.
The following Pearl Indices in women 18-35 years of age were found in the pivotal EU/Russia study based on a total of 14,759 cycles in which cycles with back-up contraception and cycles with no sexual activity have been excluded: Method failure: 0.26 (upper limit 95% confidence interval 0.77); Method and user failure: 0.44 (upper limit 95% confidence interval 1.03).
The study in the US found higher Pearl Indices than noted in the EU/Russia study. It is known that Pearl Indices of studies performed in the US are higher than noted in EU studies, but the cause of this discrepancy is unknown.
In a randomised open-label study, 97% of women in the Nextstellis group demonstrated a return to ovulation by the end of the post-treatment cycle.
Endometrial histology was investigated in a subgroup of women (n=108) in one clinical study after up to 13 cycles of treatment. There were no abnormal results.
Paediatric population: The European Medicines Agency has deferred the obligation to submit the results of studies with Nextstellis in one or more subsets of the paediatric population in oral contraception (see Dosage & Administration for information on paediatric use).
Pharmacokinetics: Estetrol: Absorption: Estetrol is rapidly absorbed after ingestion. After intake of Nextstellis, average peak plasma concentrations of 17.9 ng/mL are reached 0.5-2 hours after single ingestion.
The overall exposure to estetrol is similar irrespective of food intake. The Cmax of estetrol is reduced with approximately 50% after food intake.
Distribution: Estetrol does not bind to SHBG. Estetrol displayed moderate binding to human plasma proteins (45.5% to 50.4%) and human serum albumin (58.6%), and low binding to human alpha-glycoprotein (11.2%). Estetrol is equally distributed between red blood cells and plasma.
In vitro studies indicated that estetrol is a substrate of P-gp and BCRP transporters. Co-administration of drugs that affect the activity of P-gp and BCRP is however unlikely to result in a clinically relevant drug interaction with estetrol.
Biotransformation: After oral administration, estetrol undergoes extensive phase 2 metabolism to form glucuronide and sulphate conjugates. The two main metabolites estetrol-3-glucuronide and estetrol-16-glucuronide have negligible oestrogenic activity. UGT2B7 is the dominant UGT isoform involved in the biotransformation of estetrol into a direct glucuronide. Estetrol undergoes sulfation, mainly by specific oestrogen sulfotransferase (SULT1E1).
Elimination: The terminal elimination half-life (t½) of estetrol was observed to be around 24 hours under steady state conditions.
Following administration of a single oral solution of 15 mg [14C]-estetrol, approximately 69% of the total recovered radioactivity was detected in urine and 21.9% in faeces.
Linearity/non-linearity: When Nextstellis is administered from 1 to 5 times the dose, estetrol plasma levels do not show any relevant deviation from dose-proportionality, after single administration as well as in steady-state conditions.
Steady-state conditions: Steady-state is achieved after 5 days. Cmax of estetrol is about 17.9 ng/mL and is reached 0.5-2 hours after dosing. Average serum concentrations are 2.46 ng/mL. The accumulation is very limited with daily area under the curve (AUC) at steady-state 60% larger than after a single dose.
Drospirenone: Absorption: Drospirenone is rapidly and almost completely absorbed. After intake of Nextstellis, Cmax of about 48.7 ng/mL is reached at about 1-3 h after multiple ingestion. Bioavailability is between 76 and 85%. The overall exposure to drospirenone is similar regardless of food intake around tablet intake of Nextstellis.
Distribution: Drospirenone is bound to serum albumin and does not bind to SHBG or CBG. Only 3-5% of the total serum concentrations of the active substance are present as free steroid. The mean apparent volume of distribution of drospirenone is 3.7 ± 1.2 L/kg.
Biotransformation: Drospirenone is extensively metabolised after oral administration. The major metabolites in plasma are the acid form of drospirenone, generated by opening of the lactone ring, and the 4,5-dihydro-drospirenone-3-sulfate, formed by reduction and subsequent sulfation. Drospirenone is also subject to oxidative metabolism catalyzed by CYP3A4.
Elimination: After oral administration of Nextstellis, serum drospirenone levels decrease with a terminal elimination half-life observed around 34 hours. The metabolic clearance rate of drospirenone in serum is 1.5 ± 0.2 mL/min/kg. Drospirenone is excreted only in trace amounts in unchanged form. The metabolites of drospirenone are excreted with the faeces and urine at an excretion ratio of about 1.2 to 1.4. The t½ of metabolite excretion with the urine and faeces is about 40 h.
Linearity/non-linearity: Drospirenone plasma levels do not show any relevant deviation from dose-proportionality over the 3-15 mg dose range, after single administration as well as in steady-state conditions.
Steady-state conditions: Steady-state is achieved after 10 days. Cmax of drospirenone of about 48.7 ng/mL is reached after about 1-3 hours after dosing. The mean concentration during steady state over a 24-hour dosing period is approximately 22 ng/mL. The accumulation is very limited with daily AUC at steady-state 80% larger than after a single dose.
Special populations: Renal impairment: No studies were performed to evaluate the effect of renal disease on the pharmacokinetics of estetrol. In a study performed with drospirenone 3 mg alone administered orally for 14 days, steady-state serum drospirenone levels in women with mild renal impairment (creatinine clearance (CLcr)=50-80 mL/min) were comparable to those of women with normal renal function. The serum drospirenone levels were on average 37% higher in women with moderate renal impairment (CLcr=30-50 mL/min) compared with those in women with normal renal function.
Hepatic impairment: No studies were conducted to evaluate the effect of hepatic disease on the pharmacokinetics of estetrol. In a single dose study, oral clearance of drospirenone (CL/F) was decreased approximately 50% in volunteers with moderate hepatic impairment as compared to those with normal liver function.
Paediatric population: The pharmacokinetics of estetrol and drospirenone in postmenarcheal female adolescents (below 16 years of age) after intake of Nextstellis have not been investigated.
Other special populations: Ethnic groups: No clinically relevant differences in the pharmacokinetics of estetrol or drospirenone between Japanese and Caucasian women have been observed after single dose administration of Nextstellis.
Toxicology: Preclinical safety data: Repeated dose toxicity studies with estetrol, drospirenone or the combination have indicated expected estrogenic and gestagen effects.
At exposures exceeding those in users of Nextstellis (~27-fold multiple for estetrol and ~3.5-fold multiple for drospirenone), ventricular histological changes, without clinical effects, were observed in monkeys after repeated administration of the combination.
Reproductive toxicity studies in rats and rabbits performed with estetrol have shown embryotoxic and fetotoxic effects in animals at clinically relevant exposures; the effects possibly dependent on uterotonic effects in late gestation.
Genotoxicity and carcinogenicity studies were not conducted with the combination. Estetrol and drospirenone are not considered to be genotoxic. However, it is known that due to their hormonal action, sex steroids can promote the growth of certain hormone-dependent tissues and tumours.
Environmental risk assessment studies with drospirenone have shown that drospirenone has the potential of posing a risk to the aquatic environment (see Special precautions for disposal under Cautions for Usage).
