CLINICAL PHARMACOLOGY
PROMETRIUM Capsules are an oral dosage form of micronized progesterone which is chemically
identical to progesterone of ovarian origin. The oral bioavailability of progesterone is increased
through micronization.
Pharmacokinetics
Absorption
After oral administration of progesterone as a micronized soft-gelatin capsule formulation, maximum
serum concentrations were attained within 3 hours. The absolute bioavailability of micronized
progesterone is not known. Table 1 summarizes the mean pharmacokinetic parameters in postmenopausal
women after five oral daily doses of PROMETRIUM Capsules 100 mg as a micronized soft-gelatin
capsule formulation.
TABLE 1. Pharmacokinetic Parameters of PROMETRIUM Capsules
Parameter |
PROMETRIUM Capsules Daily Dose |
100 mg |
200 mg |
300 mg |
Cmax (ng/mL) |
17.3 ± 21.9a |
38.1 ± 37.8 |
60.6 ± 72.5 |
Tmax (hr) |
1.5 ± 0.8 |
2.3 ± 1.4 |
1.7 ± 0.6 |
AUC(0-10) (ng x hr/mL) |
43.3 ± 30.8 |
101.2 ± 66.0 |
175.7 ± 170.3 |
aMean ± S.D. |
Serum progesterone concentrations appeared linear and dose proportional following multiple dose
administration of PROMETRIUM Capsules 100 mg over the dose range 100 mg per day to 300 mg per
day in postmenopausal women. Although doses greater than 300 mg per day were not studied in
females, serum concentrations from a study in male volunteers appeared linear and dose proportional
between 100 mg per day and 400 mg per day. The pharmacokinetic parameters in male volunteers were
generally consistent with those seen in postmenopausal women.
Distribution
Progesterone is approximately 96 percent to 99 percent bound to serum proteins, primarily to serum
albumin (50 to 54 percent) and transcortin (43 to 48 percent).
Metabolism
Progesterone is metabolized primarily by the liver largely to pregnanediols and pregnanolones.
Pregnanediols and pregnanolones are conjugated in the liver to glucuronide and sulfate metabolites.
Progesterone metabolites which are excreted in the bile may be deconjugated and may be further
metabolized in the intestine via reduction, dehydroxylation, and epimerization.
Excretion
The glucuronide and sulfate conjugates of pregnanediol and pregnanolone are excreted in the bile and
urine. Progesterone metabolites are eliminated mainly by the kidneys. Progesterone metabolites which
are excreted in the bile may undergo enterohepatic recycling or may be excreted in the feces.
Special Populations
The pharmacokinetics of PROMETRIUM Capsules have not been assessed in low body weight or
obese patients.
Hepatic Insufficiency
The effect of hepatic impairment on the pharmacokinetics of PROMETRIUM
Capsules has not been studied.
Renal Insufficiency
The effect of renal impairment on the pharmacokinetics of PROMETRIUM
Capsules has not been studied.
Food–Drug Interaction
Concomitant food ingestion increased the bioavailability of PROMETRIUM Capsules relative to a
fasting state when administered to postmenopausal women at a dose of 200 mg.
Drug Interactions
The metabolism of progesterone by human liver microsomes was inhibited by ketoconazole (IC50 < 0.1
μM). Ketoconazole is a known inhibitor of cytochrome P450 3A4, hence these data suggest that
ketoconazole or other known inhibitors of this enzyme may increase the bioavailability of progesterone.
The clinical relevance of the in vitro findings is unknown.
Coadministration of conjugated estrogens and PROMETRIUM Capsules to 29 postmenopausal women
over a 12-day period resulted in an increase in total estrone concentrations (Cmax 3.68 ng/mL to 4.93
ng/mL) and total equilin concentrations (Cmax 2.27 ng/mL to 3.22 ng/mL) and a decrease in circulating
17β estradiol concentrations (Cmax 0.037 ng/mL to 0.030 ng/mL). The half-life of the conjugated
estrogens was similar with coadministration of PROMETRIUM Capsules. Table 2 summarizes the
pharmacokinetic parameters.
TABLE 2. Mean (± S.D.) Pharmacokinetic Parameters for Estradiol, Estrone, and Equilin
Following Coadministration of Conjugated Estrogens 0.625 mg and PROMETRIUM Capsules
200 mg for 12 Days to Postmenopausal Women
|
Conjugated Estrogens |
Conjugated Estrogens plus PROMETRIUM Capsules |
Drug |
Cmax(ng/mL) |
Tmax(hr) |
AUC(0-24h) (ng × h/mL) |
Cmax(ng/mL) |
Tmax(hr) |
AUC(0-24h) (ng × h/mL) |
Estradiol |
0.037 ± 0.048 |
12.7 ± 9.1 |
0.676 ± 0.737 |
0.030 ± 0.032 |
17.32 ± 1.21 |
0.561 ± 0.572 |
Estrone | 3.68 | 10.6 | 61.3 | 4.93 | 7.5 | 85.9 |
Tota1a |
± 1.55 | ± 6.8 | ± 26.36 | ± 2.07 | ± 3.8 | ± 41.2 |
EQBrlin | 2.27 | 6.0 | 28.8 | 3.22 | 5.3 | 38.1 |
Totala |
± 0.95 |
± 4.0 |
± 13.0 |
± 1.13 |
± 2.6 |
± 20.2 |
aTotal estrogens is the sum of conjugated and unconjugated estrogen. |
Clinical Studies
Effects On The Endometrium
In a randomized, double-blind clinical trial, 358 postmenopausal women, each with an intact uterus,
received treatment for up to 36 months. The treatment groups were: PROMETRIUM Capsules at the
dose of 200 mg per day for 12 days per 28-day cycle in combination with conjugated estrogens 0.625
mg per day (n=120); conjugated estrogens 0.625 mg per day only (n=119); or placebo (n=119). The
subjects in all three treatment groups were primarily Caucasian women (87 percent or more of each
group). The results for the incidence of endometrial hyperplasia in women receiving up to 3 years of
treatment are shown in Table 3. A comparison of the PROMETRIUM Capsules plus conjugated
estrogens treatment group to the conjugated estrogens only group showed a significantly lower rate of
hyperplasia (6 percent combination product versus 64 percent estrogen alone) in the PROMETRIUM
Capsules plus conjugated estrogens treatment group throughout 36 months of treatment.
TABLE 3. Incidence of Endometrial Hyperplasia in Women Receiving 3 Years of Treatment
Endometrial Diagnosis |
Treatment Group |
|
Conjugated Estrogens
0.625 mg +
PROMETRIUM
Capsules 200 mg
(cyclical) |
Conjugated Estrogens
0.625 mg
(alone) |
Placebo |
Number of patients |
% of
patients |
Number of patients |
% of patients |
Number of patients |
% of patients |
n=117 |
n=115 |
n=116 |
HYPERPLASIA a |
7 |
6 |
74 |
64 |
3 |
3 |
align="center">
Adenocarcinoma |
0 |
0 |
0 |
0 |
1 |
1 |
Atypical hyperplasia |
1 |
1 |
14 |
12 |
0 |
0 |
Complex hyperplasia |
0 |
0 |
27 |
23 |
1 |
1 |
Simple hyperplasia |
6 |
5 |
33 |
29 |
1 |
1 |
aMost advanced result to least advanced result:
Adenocarcinoma > atypical hyperplasia > complex hyperplasia > simple hyperplasia |
The times to diagnosis of endometrial hyperplasia over 36 months of treatment are shown in Figure 1.
This figure illustrates graphically that the proportion of patients with hyperplasia was significantly
greater for the conjugated estrogens group (64 percent) compared to the conjugated estrogens plus
PROMETRIUM Capsules group (6 percent).
Figure 1. Time to Hyperplasia in Women Receiving up to 36 Months of Treatment
The discontinuation rates due to hyperplasia over the 36 months of treatment are as shown in Table 4.
For any degree of hyperplasia, the discontinuation rate for patients who received conjugated estrogens
plus PROMETRIUM Capsules was similar to that of the placebo only group, while the discontinuation
rate for patients who received conjugated estrogens alone was significantly higher. Women who
permanently discontinued treatment due to hyperplasia were similar in demographics to the overall study
population.
TABLE 4. Discontinuation Rate Due to Hyperplasia Over 36 Months of Treatment
Most Advanced
Biopsy Result
Through 36 Months
of Treatment |
Treatment Group |
|
Conjugated Estrogens +
PROMETRIUM
Capsules
(cyclical) |
Conjugated Estrogens
(alone) |
Placebo |
n=120 |
n=119 |
n=119 |
Number of patients |
% of patients |
Number of patients |
% of patients |
Number of patients |
% of patients |
Adenocarcinoma |
0 |
0 |
0 |
0 |
1 |
1 |
Atypical hyperplasia |
1 |
1 |
10 |
8 |
0 |
0 |
Complex hyperplasia |
0 |
0 |
21 |
18 |
1 |
1 |
Simple hyperplasia |
1 |
1 |
13 |
11 |
0 |
0 |
Effects On Secondary Amenorrhea
In a single-center, randomized, double-blind clinical study that included premenopausal women with
secondary amenorrhea for at least 90 days, administration of 10 days of PROMETRIUM Capsules
therapy resulted in 80 percent of women experiencing withdrawal bleeding within 7 days of the last
dose of PROMETRIUM Capsules, 300 mg per day (n=20), compared to 10 percent of women
experiencing withdrawal bleeding in the placebo group (n=21).
In a multicenter, parallel-group, open label, postmarketing dosing study that included premenopausal
women with secondary amenorrhea for at least 90 days, administration of 10 days of PROMETRIUM
Capsules during two 28-day treatment cycles, 300 mg per day (n=107) or 400 mg per day (n=99),
resulted in 73.8 percent and 76.8 percent of women, respectively, experiencing withdrawal bleeding.
The rate of secretory transformation was evaluated in a multicenter, randomized, double-blind clinical
study in estrogen-primed postmenopausal women. PROMETRIUM Capsules administered orally for 10
days at 400 mg per day (n=22) induced complete secretory changes in the endometrium in 45 percent of
women compared to 0 percent in the placebo group (n=23).
A second multicenter, parallel-group, open label postmarketing dosing study in premenopausal women
with secondary amenorrhea for at least 90 days also evaluated the rate of secretory transformation. All
subjects received daily oral conjugated estrogens over 3 consecutive 28-day treatment cycles and
PROMETRIUM Capsules, 300 mg per day (n=107) or 400 mg per day (n=99) for 10 days of each
treatment cycle. The rate of complete secretory transformation was 21.5 percent and 28.3 percent,
respectively.
Women's Health Initiative Studies
The Women's Health Initiative (WHI) enrolled approximately 27,000 predominantly healthy
postmenopausal women in two substudies to assess the risks and benefits of daily oral conjugated
estrogens (CE) [0.625 mg]-alone or in combination with medroxyprogesterone acetate (MPA) [2.5 mg]
compared to placebo in the prevention of certain chronic diseases. The primary endpoint was the
incidence of coronary heart disease [(CHD) defined as nonfatal myocardial infarction (MI), silent MI
and CHD death], with invasive breast cancer as the primary adverse outcome. A “global index” included
the earliest occurrence of CHD, invasive breast cancer, stroke, pulmonary embolism (PE), endometrial
cancer (only in the CE plus MPA substudy), colorectal cancer, hip fracture, or death due to other cause.
These sub studies did not evaluate the effects of CE–alone or CE plus MPA on menopausal symptoms.
WHI Estrogen Plus Progestin Substudy
The WHI estrogen plus progestin substudy was stopped early. According to the predefined stopping
rule, after an average follow-up of 5.6 years of treatment, the increased risk of breast cancer and
cardiovascular events exceeded the specified benefits included in the “global index.” The absolute
excess risk of events in the “global index” was 19 per 10,000 women-years.
For those outcomes included in the WHI “global index” that reached statistical significance after 5.6
years of follow-up, the absolute excess risks per 10,000 women-years in the group treated with CE
plus MPA were 7 more CHD events, 8 more strokes, 10 more PEs, and 8 more invasive breast cancers,
while the absolute risk reductions per 10,000 women-years were 6 fewer colorectal cancers and 5
fewer hip fractures.
Results of the estrogen plus progestin substudy, which included 16,608 women (average 63 years of
age, range 50 to 79; 83.9 percent White, 6.8 percent Black, 5.4 percent Hispanic, 3.9 percent Other) are
presented in Table 5. These results reflect centrally adjudicated data after an average follow-up of 5.6
years.
TABLE 5. Relative and Absolute Risk Seen in the Estrogen Plus Progestin Substudy of WHI at
an Average of 5.6 Years a, b
Events |
Relative Risk
CE/MPA versus
Placebo (95% nCIc) |
CE/MPA
n = 8,506 |
Placebo
n = 8,102 |
Absolute Risk per
10,000 Women-Years |
CHD events |
1.23 (0.99-1.53) |
41 |
34 |
Non-fatal MI |
1.28 (1.00-1.63) |
31 |
25 |
CHD death |
1.10 (0.70-1.75) |
8 |
8 |
All stroke |
1.31 (1.03-1.88) |
33 |
25 |
align="center">
Ischemic Stroke |
1.44 (1.09-1.90) |
26 |
18 |
Deepvein thrombosisd |
1.95 (1.43-2.67) |
26 |
13 |
Pulmonary embolism |
2.13 (1.45-3.11) |
18 |
8 |
Invasive breast cancer e |
1.24 (1.01-1.54) |
41 |
33 |
Colorectal cancer |
0.61 (0.42-0.87) |
10 |
16 |
Endometrial cancer d |
0.81 (0.48-1.36) |
6 |
7 |
Cervical cancer d |
1.44 (0.47-4.42) |
2 |
1 |
Hip fracture |
0.67 (0.47-0.96) |
11 |
16 |
Vertebral fractures d |
0.65 (0.46-0.92) |
11 |
17 |
Lower arm/wrist fractures d |
0.71 (0.59-0.85) |
44 |
62 |
Total fractures d |
0.76 (0.69-0.83) |
152 |
199 |
Overall mortality f |
1.00 (0.83-1.19) |
52 |
52 |
Global Index g |
1.13 (1.02-1.25) |
184 |
165 |
aAdapted from numerous WHI publications. WHI publications can be viewed at
www.nhlbi.nih.gov/whi.
bResults are based on centrally adjudicated data.
cNominal confidence intervals unadjusted for multiple looks and multiple comparisons.
dNot included in Global Index.
eIncludes metastatic and non-metastatic breast cancer with the exception of in situ breast cancer.
fAll deaths, except from breast or colorectal cancer, definite or probable CHD, PE or cerebrovascular
disease.
gA subset of the events was combined in a “global index” defined as the earliest occurrence of CHD
events, invasive breast cancer, stroke, pulmonary embolism, endometrial cancer, colorectal cancer, hip
fracture, or death due to other causes. |
Timing of the initiation of estrogen plus progestin therapy relative to the start of menopause may affect
the overall risk benefit profile. The WHI estrogen plus progestin substudy stratified for age showed in
women 50 to 59 years of age a non-significant trend toward reducing risk of overall mortality [hazard
ratio (HR) 0.69 (95 percent CI, 0.44-1.07)].
Women's Health Initiative Memory Study
The estrogen plus progestin Women's Health Initiative Memory Study (WHIMS), an ancillary study of
WHI, enrolled 4,532 predominantly healthy postmenopausal women 65 years of age and older (47
percent were 65 to 69 years of age; 35 percent were 70 to 74 years of age; and 18 percent were 75
years of age and older) to evaluate the effects of daily CE (0.625 mg) plus MPA (2.5 mg) on the
incidence of probable dementia (primary outcome) compared to placebo.
After an average follow-up of 4 years, the relative risk of probable dementia for CE plus MPA versus
placebo was 2.05 (95 percent CI, 1.21 – 3.48). The absolute risk of probable dementia for CE plus MPA
versus placebo was 45 versus 22 per 10,000 women-years. Probable dementia as defined in this study
included Alzheimer's disease (AD), vascular dementia (VaD) and mixed type (having features of both
AD and VaD). The most common classification of probable dementia in the treatment group and the
placebo group was AD. Since the ancillary study was conducted in women 65 to 79 years of age, it is
unknown whether these findings apply to younger postmenopausal women. (See WARNINGS,
Probable dementia and PRECAUTIONS, Geriatric Use.)