Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1      Pharmacodynamic properties
Pharmacotherapeutic group (ATC): Progestogens and estrogens, fixed combinations ATC Code: G03AA12

Pearl Index for method failure: 0.41 (upper two-sided 95 % confidence limit: 0.85) Overall Pearl Index (method failure + patient failure): 0.80 (upper two-sided 95% confidence limit: 1.30)

The contraceptive effect of YAZ is based on the interaction of various factors, the most important of which are seen as the inhibition of ovulation and the changes in the endometrium.

In a 3-cycle ovulation inhibition study comparing drospirenone 3 mg / ethinylestradiol 0.020 mg in a 24-day-regimen and a 21-day-regimen, the 24-day-regimen was associated with greater suppression of follicular development. After intentionally introduced dosing errors during the third cycle of treatment, a greater proportion of women in the 21-day-regimen showed ovarian activity including escape ovulations compared to the women taking the 24-day-regimen. Ovarian activity returned to pre-treatment levels during the post-treatment cycle in 91.8% of the women who took the 24-day regimen.

YAZ is a combined oral contraceptive with ethinylestradiol and the progestogen drospirenone. In a therapeutic dosage, drospirenone also possesses antiandrogenic and mild antimineralocorticoid properties. It has no estrogenic, glucocorticoid and antiglucocorticoid activity. This gives drospirenone a pharmacological profile closely resembling the natural hormone progesterone.

There are indications from clinical studies that the mild antimineralocorticoid properties of YAZ result in a mild antimineralocorticoid effect.

Two multicenter, double blind, randomized, placebo controlled studies were performed to evaluate the efficacy and safety of YAZ in women with moderate acne vulgaris.

After six months of treatment, in comparison with placebo, YAZ showed a statistically significantly greater reduction of 15.6% (49.3% versus 33.7%) in inflammatory lesions, 18.5% (40.6% versus 22.1%) in non-inflammatory lesions, and 16.5% (44.6% versus 28.1%) in total lesion counts. In addition, a higher percentage of subjects, 11.8% (18.6% versus 6.8%), showed a ‘clear’ or ‘almost clear’ rating on the Investigator’s Static Global Assessment (ISGA) scale.

Pharmacokinetic Properties

5.2      Pharmacokinetic properties

•     Drospirenone
Absorption
Orally administered drospirenone is rapidly and almost completely absorbed. Maximum concentrations of the active substance in serum of about 38 ng/ml are reached at about 1-2 h after single ingestion. Bioavailability is between 76 and 85 %. Concomitant ingestion of food has no influence on the bioavailability of drospirenone.

Distribution
After oral administration, serum drospirenone levels decrease with a terminal half-life of 31 h.
Drospirenone is bound to serum albumin and does not bind to sex hormone binding globulin (SHBG) or corticoid binding globulin (CBG). Only 3 - 5 % of the total serum concentrations of the active substance are present as free steroid. The ethinylestradiol-induced increase in SHBG does not influence the serum protein binding of drospirenone. The mean apparent volume of distribution of drospirenone is 3.7 ± 1.2 l/kg.

Biotransformation
Drospirenone is extensively metabolized 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 sulfatation. Drospirenone is also subject to oxidative metabolism catalyzed by CYP3A4.

Elimination
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 half-life of metabolite excretion with the urine and faeces is about 40h.

Steady-State Conditions
During a treatment cycle, maximum steady-state concentrations of drospirenone in serum of about 70 ng/ml are reached after about 8 days of treatment. Serum drospirenone levels accumulated by a factor of about 3 as a consequence of the ratio of terminal half-life and dosing interval.

Special Populations
Effect of renal impairment
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 to those in women with normal renal function. Drospirenone treatment was also well tolerated by women with mild and moderate renal impairment.
Drospirenone treatment did not show any clinically significant effect on serum potassium concentration.

Effect of hepatic impairment
In a single dose study, oral clearance (CL/F) was decreased approximately 50 % in volunteers with moderate hepatic impairment as compared to those with normal liver function. The observed decline in drospirenone clearance in volunteers with moderate hepatic impairment did not translate into any apparent difference in terms of serum potassium concentrations. Even in the presence of diabetes and concomitant treatment with spironolactone (two factors that can predispose a patient to hyperkalemia) an increase in serum potassium concentrations above the upper limit of the normal range was not observed. It can be concluded that drospirenone is well tolerated in patients with mild or moderate hepatic impairment (Child-Pugh B).

Ethnic groups
No clinically relevant differences in the pharmacokinetics of drospirenone or ethinylestradiol between Japanese and Caucasian women have been observed.

•   Ethinylestradiol

Absorption
Orally administered ethinylestradiol is absorbed rapidly and completely. Peak serum concentrations of about 33 pg/ml are reached within 1 - 2 hours after single oral administration.
Absolute bioavailability as a result of presystemic conjugation and first-pass metabolism is approximately 60 %. Concomitant intake of food reduced the bioavailability of ethinylestradiol in about 25 % of the investigated subjects while no change was observed in the others.
Distribution
Serum ethinylestradiol levels decrease in two phases, the terminal disposition phase is characterized by a half-life of approximately 24 hours. Ethinylestradiol is highly but non-specifically bound to serum albumin (approximately 98.5 %), and induces an increase in the serum concentrations of SHBG and corticoid binding globulin (CBG). An apparent volume of distribution of about 5 l/kg was determined.

Biotransformation
Ethinylestradiol is subject to significant gut and hepatic first-pass metabolism. Ethinylestradiol is primarily metabolized by aromatic hydroxylation but a wide variety of hydroxylated and methylated metabolites are formed, and these are present as free metabolites and as conjugates with glucuronides and sulfate. The metabolic clearance rate of ethinylestradiol is about 5 ml/min/kg.

In vitro ethinylestradiol is a reversible inhibitor of CYP2C19, CYP1A1 and CYP1A2 as well as a mechanism based inhibitor of CYP3A4/5, CYP2C8 and CYP2J2.


Elimination
Ethinylestradiol is not excreted in unchanged form to any significant extent. The metabolites of ethinylestradiol are excreted at a urinary to biliary ratio of 4:6. The half-life of metabolite excretion is about 1 day.

Steady-state conditions
Steady-state conditions are reached during the second half of a treatment cycle and serum levels of ethinylestradiol accumulate by a factor of about 2.0 to 2.3.