CLINICAL PHARMACOLOGY
Mechanism Of Action
COCs lower the risk of becoming pregnant primarily by
suppressing ovulation. Other possible mechanisms may include cervical mucus
changes that inhibit sperm penetration and endometrial changes that reduce the
likelihood of implantation.
Pharmacodynamics
The estrogen in Natazia is estradiol valerate, a
synthetic prodrug of 17Ã-estradiol. The progestin in Natazia is dienogest
(DNG). DNG displays properties of 19-nortestosterone derivatives as well as
properties associated with progesterone derivatives. [See Nonclinical
Toxicology]
Cardiac Electrophysiology
The effect of Natazia on QT prolongation was evaluated in
a randomized, double-blind, positive (moxifloxacin 400 mg) and negative
(placebo) controlled crossover study in healthy subjects. A total of 53
subjects were administered Natazia (containing 3 mg dienogest and 2 mg
estradiol valerate), dienogest 10 mg, and placebo as once daily doses for 4
days, and moxifloxacin 400 mg as a single oral dose. The upper bound of the 90%
confidence interval for the largest placebo-adjusted, baseline-corrected QTc
based on Fridericia's correction method (QTcF) was below 10 msec, the threshold
for regulatory concern.
Pharmacokinetics
Absorption
After oral administration of estradiol valerate, cleavage
to 17β-estradiol and valeric acid takes place during absorption by the
intestinal mucosa or in the course of the first liver passage. This gives rise
to estradiol and its metabolites, estrone and other metabolites. Maximum serum
estradiol concentrations of 73.3 pg/mL are reached at a median of approximately
6 hours (range: 1.5–12 hours) and the area under the estradiol concentration
curve [AUC(0–24h)] was 1301 pg·h/mL after single ingestion of a tablet
containing 3 mg estradiol valerate under fasted condition on Day 1 of the
28-day sequential regimen.
Bioavailability of dienogest is about 91%. Maximum serum
dienogest concentrations of 91.7 ng/mL are reached at a median of approximately
1 hour (range: 0.5–1.5 hour) and the area under the dienogest concentration
curve [AUC(0– 24h)] was 964 ng/mL after single oral administration of Natazia
tablet containing 2 mg estradiol valerate/3 mg dienogest under fasted
condition. The pharmacokinetics of dienogest are dose-proportional within the
dose range of 1–8 mg. Steady state is reached after 4 days of the same dosage
of 2 mg dienogest. The mean accumulation ratio for AUC (0–24h) is approximately
1.24.
The mean plasma pharmacokinetic parameters at steady
state following repeated oral doses of a 2 mg estradiol valerate/3 mg dienogest
combination tablet in fertile women under fasted condition are reported in
Table 1.
Table 1: Arithmetic Mean (SD) Serum
Pharmacokinetic Parameters at Steady-state (on Day 24) following Repeated Oral
Doses of 2 mg EV/3 mg DNG on Days 8–24 of the 28 day Regimen in Fertile Women
under Fasted Condition (N=15)
Parameter |
Dienogest |
Estradiol |
Estrone |
C |
85.2 (19.7) ng/ml |
70.5 (25.9) pg/ml |
483 (198) pg/ml |
Tmax (h)a |
1.5 (1-2) |
3 (1.5-12) |
4 (3-12) |
AUC(0-24h) |
828 (187) ngh/ml |
1323 (480) pg•h/ml |
7562 (3403) pg•h/ml |
t½ (h) |
12.3 (1.4) |
NA |
NA |
a Median (range) for Tmax
Cmax = Maximum serum concentration
Tmax = Time to reach maximum concentration
AUC(0–24h) = Area under the concentration-time curve from 0 h data point up to
48 h post-administration
NA: Data not available |
Food Effect
Concomitant food intake in
women resulted in a 28% decrease for dienogest Cmax and 23% increase of
estradiol Cmax while the exposure (AUC) of both dienogest and estradiol did not
change.
Distribution
In serum, 38% of estradiol is bound to sex
hormone-binding globulin (SHBG), 60% to albumin and 2–3% circulates in free
form. An apparent volume of distribution of approximately 1.2 L/kg was
determined after intravenous (IV) administration.
A relatively high fraction (10%) of circulating dienogest
is present in the free form, with approximately 90% being bound
non-specifically to albumin. Dienogest does not bind to SHBG and
corticosteroid-binding globulin (CBG). The volume of distribution at steady
state (Vd,ss) of dienogest is 46 L after the IV administration of 85 mcg 3H-dienogest.
Metabolism
After oral administration of estradiol valerate,
approximately 3% of the dose is directly bioavailable as estradiol. Estradiol
undergoes an extensive first-pass effect and a considerable part of the dose
administered is already metabolized in the gastrointestinal mucosa. The CYP 3A
family is known to play the most important role in human estradiol metabolism.
Together with the pre-systemic metabolism in the liver, about 95% of the orally
administered dose becomes metabolized before entering the systemic circulation.
The main metabolites are estrone and its sulfate or glucuronide conjugates.
Dienogest is extensively metabolized by the known
pathways of steroid metabolism (hydroxylation, conjugation), with the formation
of endocrinologically mostly inactive metabolites. CYP3A4 was identified as a
predominant enzyme catalyzing the metabolism of dienogest.
Excretion
Estradiol and its metabolites are mainly excreted in
urine, with about 10% being excreted in the feces. The terminal half-life of
estradiol is approximately 14 hours.
Dienogest is mainly excreted renally in the form of
metabolites and unchanged dienogest is the dominating fraction in plasma. The
terminal half-life of dienogest is approximately 11 hours.
Use in Specific Populations
Pediatric Use: Safety and efficacy of
Natazia has been established in women of reproductive age. Efficacy is expected
to be the same for postpubertal adolescents under the age of 18 and for users
18 years and older. Use of this product before menarche is not indicated.
Geriatric Use: Natazia has not been studied
in postmenopausal women and is not indicated in this population
Renal Impairment: The pharmacokinetics of
Natazia has not been studied in subjects with renal impairment.
Hepatic Impairment: The pharmacokinetics of
Natazia has not been studied in subjects with hepatic impairment. Steroid
hormones may be poorly metabolized in patients with impaired liver function.
Acute or chronic disturbances of liver function may necessitate the discontinuation
of COC use until markers of liver function return to normal. [See CONTRAINDICATIONS
and WARNINGS AND PRECAUTIONS]
Body Mass Index: The efficacy of Natazia in
women with a BMI of > 30 kg/m² has not been evaluated.
Drug Interactions
Consult the labeling of all concurrently used drugs to
obtain further information about interactions with oral contraceptives or the
potential for enzyme alterations.
Effects of Other Drugs on Combined Oral Contraceptives
Substances diminishing the efficacy of COCs: Dienogest
is a substrate of CYP3A4.
Drugs or herbal products that induce certain enzymes,
including CYP3A4, may decrease the effectiveness of COCs or increase
breakthrough bleeding.
The effect of the CYP3A4 inducer rifampicin was studied
in an open-label, non-randomized, single center study in 16 healthy
postmenopausal women. All volunteers received a treatment regimen of 2 mg
estradiol valerate and 3 mg dienogest combination tablets, dosed once daily
over 17 days, and of rifampicin, which was administered once daily in an oral
dose of 600 mg on Days 12 to 16.Twenty-four-hour (24h) pharmacokinetics of
estradiol and dienogest on Days 11 and 17 were compared. Co-administration of
rifampicin with estradiol valerate/dienogest tablets led to a 52 % and 83%
decrease in the mean Cmax and AUC(0–24h), respectively, for dienogest and a 25%
and 44% decrease in Cmax and AUC(0– 24h), respectively, for estradiol at steady
state.
Substances Increasing the Systemic Exposure of COCs (enzyme
inhibitors): The effect of a strong CYP3A4 inhibitor, ketoconazole, on
dienogest and estradiol exposure was studied in an open-label, one-sequence,
one-way crossover study in healthy postmenopausal Caucasian women. One tablet
of 2 mg estradiol valerate and 3 mg dienogest was administered orally once a
day for 14 days. Twelve volunteers received an oral dose of 400 mg ketoconazole
(that is, 2 tablets containing 200 mg ketoconazole) once daily for 7 days (Days
8–14). Twenty-four hour pharmacokinetics of estradiol and dienogest on Days 7
and 14 were compared. Co-administration with the strong inhibitor ketoconazole
increased the AUC (0–24h) at steady state for dienogest and estradiol by 2.86
and 1.57-fold, respectively. There was also a 1.94 and 1.65-fold increase of Cmax
at steady state for dienogest and estradiol when coadministered with
ketoconazole.
The effect of a moderate CYP3A4 inhibitor, erythromycin
on dienogest and estradiol exposure was studied in an open-label, one-sequence,
one-way crossover study in healthy postmenopausal Caucasian women. One tablet
of 2 mg estradiol valerate and 3 mg dienogest was administered orally once a
day for 14 days. Twelve volunteers received an oral dose of 500 mg erythromycin
three times a day for 7 days (Days 8–14). Twenty-four hour pharmacokinetics of
estradiol and dienogest on Days 7 and 14 were compared. When co-administered
with the moderate inhibitor erythromycin, the AUC (0–24h) of dienogest and
estradiol at steady state were increased by 1.62 and 1.33-fold, respectively.
There was also a 1.33 and 1.51-fold increase of Cmax at steady state for
dienogest and estradiol, respectively, when co-administered with erythromycin.
HIV/HCV Protease Inhibitors and Non-Nucleoside Reverse Transcriptase Inhibitors
Significant changes (increase or decrease) in the plasma
concentrations of the estrogen and progestin have been noted in some cases of
co-administration of HIV/HCV protease inhibitors or with non-nucleoside reverse
transcriptase inhibitors.
Antibiotics
There have been reports of pregnancy while taking
hormonal contraceptives and antibiotics, but clinical pharmacokinetic studies
have not shown consistent effects of antibiotics on plasma concentrations of
synthetic steroids.
Effects of Combined Oral Contraceptives on Other Drugs
COCs containing ethinyl estradiol may inhibit the
metabolism of other compounds. COCs have been shown to significantly decrease
plasma concentrations of lamotrigine, likely due to induction of lamotrigine
glucuronidation. This may reduce seizure control; therefore, dosage adjustments
of lamotrigine may be necessary. Consult the labeling of the concurrently-used
drug to obtain further information about interactions with COCs or the
potential for enzyme alterations.
In vitro studies with human CYP enzymes did not indicate
an inhibitory potential of dienogest at clinically relevant concentrations.
Women on thyroid hormone replacement therapy may need
increased doses of thyroid hormone because serum concentration of
thyroid-binding globulin increases with use of COCs.
Animal Toxicology And/Or Pharmacology
Nonclinical studies in animals and in vitro, have shown
that besides progestogenic activities, DNG is devoid of estrogenic, androgenic,
glucocorticoid and mineralocorticoid activities.
Clinical Studies
Oral Contraceptive Clinical Trials
The study conducted in North America (U. S. and Canada)
was a multicenter, open-label, single-arm, unintended pregnancy study. There
were 490 healthy subjects between 18 and 35 years of age (mean age: 25.1 years)
who were treated for up to 28 cycles of 28 days each. The racial demographic of
enrolled women was: Caucasian (76%), Hispanic (13%), African-American (7%),
Asian (3%), and Other (1%). The weight range for treated women was 40 to 100 kg
(mean weight: 62.5 kg) and the BMI range was 14 to 30 kg/m² (mean
BMI: 23.3 kg/m²). Of treated women, 15% discontinued the study
treatment due to an adverse event, 13% were lost to follow up, 10% withdrew
their consent, 8% discontinued due to other reason, 1% discontinued due to
protocol deviation, and 1% discontinued due to pregnancy.
The study conducted in Europe (Germany, Austria and
Spain) was a multicenter, open-label, single-arm contraceptive reliability
study. There were 1,377 healthy subjects between 18 and 50 years of age (mean
age: 30.3 years) who were treated for 20 cycles of 28 days each. The racial
demographic of enrolled women was predominantly Caucasian (99.2%). The weight
range for treated women was 38 to 98 kg (mean weight: 63.8 kg) and the BMI
range was 15 to 31.8 kg/m² (mean BMI: 22.8 kg/m²). Of
treated women, 10% discontinued the study treatment due to an adverse event, 5%
discontinued due to other reason, 2% were lost to follow up, 2% discontinued
due to protocol deviation, 2% withdrew their consent, and 1% discontinued due
to pregnancy.
The Pearl Index (PI) was the primary efficacy endpoint
used to assess contraceptive reliability and was assessed in each of the two
studies, assuming all subjects were at risk of pregnancy in all medication
cycles unless back-up contraception was documented. The PI is based on
pregnancies that occurred after the onset of treatment and within 7 days after
the last pill intake. Cycles in which conception did not occur, but which
included the use of back-up contraception, were not included in the calculation
of the PI. The PI also includes patients who did not take the drug correctly.
The estimated PI for the North American study is 1.64 and the estimated PI for
the European study is 1.04.The Kaplan-Meier method was also used to calculate
the contraceptive failure rate.
The summary of the Pearl Indexes and cumulative
contraceptive failure rates are provided in Table 2:
Table 2: Summary of the Pearl Indexes and the
Cumulative Contraceptive Failure Rates
Study |
Age Group |
Relative Treatment Exposure Cycles1 |
Number of Pregnancies within 13 Cycles and 7 Days after Last Treatment |
Pearl Index |
Upper Limit of 95% CI |
Contraceptive Failure Rate at the End of First Year |
North America |
18-35 |
3,969 |
5 |
1.64 |
3.82 |
0.016 |
Europe |
18-35 |
11,275 |
9 |
1.04 |
1.97 |
0.010 |
1Total treatment exposure time without back-up contraception |
Heavy Menstrual Bleeding
Clinical Trials
The efficacy and safety of
Natazia were evaluated in two multi-regional, multicenter, double-blind,
randomized, placebo-controlled clinical trials. Study 308960 was performed in
the United States and Canada and Study 308961 was performed in Australia and 9
European countries. The studies were identical in design. The studies enrolled
women, 18 years of age or older, with a diagnosis of dysfunctional uterine
bleeding characterized as heavy, prolonged and/or frequent bleeding without
organic pathology. Heavy menstrual bleeding (HMB) was defined as menstrual
blood loss of 80 mL or more in at least 2 bleeding episodes. The diagnosis of
HMB was documented through the collection of used sanitary protection (pads and
tampons) to quantify blood loss assessed by the alkaline hematin method.
Overall, about 85% of the subjects qualified for the study because they had
heavy menstrual bleeding symptoms.
A total of 421 women with a
mean age of 38.2 and a mean BMI of 25.5 were randomized to the two clinical
studies, for a total of 269 women in the Natazia group and 152 women in the
placebo group, and treated for seven 28-day cycles. Approximately 81% were
Caucasian, 13% were Black, and 6% were Hispanic or Asian or Other.
The primary efficacy variable
was the proportion of subjects who were completely relieved of symptoms, which
was defined by the number of subjects with the absence of any dysfunctional
bleeding symptom and who met up to 8 strictly defined criteria for success
during the 90-day efficacy assessment phase. In Study 308960, the proportion of
the intent-totreat subjects with complete symptom relief was 29.2% in the
Natazia group compared to 2.9% in the placebo group. In Study 308961, the
proportion of the intent-to-treat subjects with complete symptom relief was
29.5% in the Natazia group compared to 1.2% in the placebo group.
In both studies, Natazia was effective in treating the
symptoms of HMB in the subset of women who entered the study with symptoms
specific to HMB. Among patients with HMB, menstrual blood loss (MBL) was
statistically significantly reduced in the group treated with Natazia compared
with placebo (p < 0.0001 for both studies). Evaluating data based on 28-day cycles,
the median menstrual blood volume at Cycle 7 was reduced from the baseline
median by 90% in one trial and 87% in the other. For women treated with
placebo, the median menstrual blood volume at Cycle 7 was reduced from the
baseline median by 14% and 32% in the two trials, respectively. Figures 1 and 2
display the MBL volume by cycle and by study.
Figure 1: Median Menstrual Blood Loss Volume by Cycle
(Study 308960)
Figure 2: Median Menstrual
Blood Loss Volume by Cycle (Study 308961)