CLINICAL PHARMACOLOGY
Endogenous estrogens are largely responsible for the
development and maintenance of the female reproductive system and secondary
sexual characteristics. Although circulating estrogens exist in a dynamic
equilibrium of metabolic interconversions, estradiol is the principal
intracellular human estrogen and is substantially more potent than its
metabolites estrone and estriol at the receptor level.
The primary source of estrogen in normally cycling adult
women is the ovarian follicle, which secretes 70 to 500 mcg of estradiol daily,
depending on the phase of the menstrual cycle. After menopause, most endogenous
estrogen is produced by conversion of androstenedione, secreted by the adrenal
cortex, to estrone by peripheral tissues. Thus, estrone and the sulfate
conjugated form, estrone sulfate, are the most abundant circulating estrogens
in postmenopausal women. The pharmacologic effects of ethinyl estradiol are
similar to those of endogenous estrogens.
Estrogens act through binding to nuclear receptors in
estrogen-responsive tissues. To date, two estrogen receptors have been
identified. These vary in proportion from tissue to tissue.
Circulating estrogens modulate the pituitary secretion of
the gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone
(FSH) through a negative feedback mechanism. Estrogens act to reduce the
elevated levels of these hormones seen in postmenopausal women.
Progestin compounds enhance cellular differentiation and
generally oppose the actions of estrogens by decreasing estrogen receptor
levels, increasing local metabolism of estrogens to less active metabolites, or
inducing gene products that blunt cellular responses to estrogen. Progestins
exert their effects in target cells by binding to specific progesterone
receptors that interact with progesterone response elements in target genes.
Progesterone receptors have been identified in the female reproductive tract,
breast, pituitary, hypothalamus, bone, skeletal tissue and central nervous
system. Progestins produce similar endometrial changes to those of the
naturally occurring hormone progesterone.
Pharmacokinetics
Absorption
Norethindrone acetate (NA) is completely and rapidly
deacetylated to norethindrone after oral administration, and the disposition of
norethindrone acetate is indistinguishable from that of orally administered
norethindrone. Norethindrone acetate and ethinyl estradiol (EE) are rapidly
absorbed from norethindrone acetate and ethinyl estradiol tablets, with maximum
plasma concentrations of norethindrone and ethinyl estradiol generally
occurring 1 to 2 hours postdose. Both are subject to firstpass metabolism after
oral dosing, resulting in an absolute bioavailability of approximately 64% for norethindrone
and 55% for ethinyl estradiol. Bioavailability of norethindrone acetate and
ethinyl estradiol tablets is similar to that from solution for norethindrone
and slightly less for ethinyl estradiol. Administration of norethindrone
acetate and ethinyl estradiol tablets with a high fat meal decreases rate but
not extent of ethinyl estradiol absorption. The extent of norethindrone
absorption is increased by 27% following administration of norethindrone
acetate and ethinyl estradiol tablets with food.
The full pharmacokinetic profile of norethindrone acetate
and ethinyl estradiol tablets was not characterized due to assay sensitivity
limitations. However, the multiple-dose pharmacokinetics were studied at a dose
of 1 mg NA/10 mcg EE in 18 post-menopausal women. Mean plasma concentrations
are shown below (Figure 1) and pharmacokinetic parameters are found in Table 1.
Based on a population pharmacokinetic analysis, mean steady-state
concentrations of norethindrone for 1 mg NA/5 mcg EE and 1/10 are slightly more
than proportional to dose when compared to 0.5 mg NA/2.5 mcg EE tablets. It can
be explained by higher sex hormone binding globulin (SHBG) concentrations. Mean
steady-state plasma concentrations of ethinyl estradiol for the norethindrone
acetate and ethinyl estradiol 0.5/2.5 tablets and norethindrone acetate and
ethinyl estradiol 1/5 tablets are proportional to dose, but there is a less
than proportional increase in steady-state concentrations for the NA/EE 1/10
tablet.
Figure 1: Mean Steady-State (Day 87) Plasma
Norethindrone and Ethinyl Estradiol Concentrations Following Continuous Oral
Administration of 1 mg NA/10 mcg EE Tablets
Table 1: Mean (SD) Single-Dos e (Day 1) and
Steady-State (Day 87) Pharmacokinetic Parameters Following Adminis tration of 1
mg NA/10 mcg EE Tablets
Norethindrone |
Cmax ng/mL |
tmax hr |
AUC(0-24) ng-hr/mL |
CL/F mL/min |
t½ hr |
Day 1 |
6.0 (3.3) |
1.8 (0.8) |
29.7 (16.5) |
588 (416) |
10.3 (3.7) |
Day 87 |
10.7 (3.6) |
1.8 (0.8) |
81.8 (36.7) |
226 (139) |
13.3 (4.5) |
Ethinyl Estradiol |
pg/mL |
hr |
pg•hr/mL |
mL/min |
hr |
Day 1 |
33.5 (13.7) |
2.2 (1.0) |
339 (113) |
ND† |
ND† |
Day 87 |
38.3 (11.9) |
1.8 (0.7) |
471 (132) |
383 (119) |
23.9 (7.1) |
*C max = Maximum plasma concentration; t max = time of C max;
AUC(0-24)= Area under the plasma concentration-time curve over the dosing interval;
and CL/F = Apparent oral clearance; t ½= Elimination half-life
†ND = Not determined |
Based on a population pharmacokinetic analysis, average
steady-state concentrations (Css) of norethindrone and ethinyl estradiol for
norethindrone acetate and ethinyl estradiol 1/5 tablets are estimated to be 2.6
ng/mL and 11.4 pg/mL, respectively. Css values of norethindrone and ethinyl estradiol
for norethindrone acetate and ethinyl estradiol 0.5/2.5 tablets are estimated
to be 1.1 ng/mL and 5.4 ng/mL, respectively.
The pharmacokinetics of ethinyl estradiol and
norethindrone acetate were not affected by age, (age range 40-62 years), in the
postmenopausal population studied.
Distribution
The distribution of exogenous estrogens is similar to
that of endogenous estrogens. Estrogens are widely distributed in the body and
are generally found in higher concentrations in the sex hormone target organs.
Estrogens circulate in the blood largely bound to sex hormone binding globulin
(SHBG) and albumin.
Volume of distribution of norethindrone and ethinyl
estradiol ranges from 2 to 4 L/kg. Plasma protein binding of both steroids is
extensive ( > 95%); norethindrone binds to both albumin and sex hormone binding
globulin (SHBG), whereas ethinyl estradiol binds only to albumin. Although
ethinyl estradiol does not bind to SHBG, it induces SHBG synthesis.
Metabolism
Exogenous estrogens are metabolized in the same manner as
endogenous estrogens. Circulating estrogens exist in a dynamic equilibrium of
metabolic interconversions. These transformations take place mainly in the
liver. Estradiol is converted reversibly to estrone, and both can be converted
to estriol, which is the major urinary metabolite. Estrogens also undergo
enterohepatic recirculation via sulfate and glucuronide conjugation in the
liver, biliary secretion of conjugates into the intestine, and hydrolysis in
the gut followed by reabsorption. In postmenopausal women, a significant
proportion of the circulating estrogens exist as sulfate conjugates, especially
estrone sulfate, which serves as a circulating reservoir for the formation of
more active estrogens.
Norethindrone undergoes extensive biotransformation,
primarily via reduction, followed by sulfate and glucuronide conjugation. The
majority of metabolites in the circulation are sulfates, with glucuronides accounting
for most of the urinary metabolites. A small amount of norethindrone acetate is
metabolically converted to ethinyl estradiol, such that exposure to ethinyl
estradiol following administration of 1 mg of norethindrone acetate is
equivalent to oral administration of 2.8 mcg ethinyl estradiol. Ethinyl estradiol
is also extensively metabolized, both by oxidation and by conjugation with
sulfate and glucuronide. Sulfates are the major circulating conjugates of
ethinyl estradiol and glucuronides predominate in urine. The primary oxidative
metabolite is 2-hydroxy ethinyl estradiol, formed by the CYP3A4 isoform of
cytochrome P450. Part of the first-pass metabolism of ethinyl estradiol is
believed to occur in gastrointestinal mucosa. Ethinyl estradiol may undergo
enterohepatic circulation.
Excretion
Estradiol, estrone, and estriol are excreted in the urine
along with glucuronide and sulfate conjugates.
Norethindrone and ethinyl estradiol are excreted in both
urine and feces, primarily as metabolites. Plasma clearance values for
norethindrone and ethinyl estradiol are similar (approximately 0.4 L/hr/kg). Steady-state
elimination half-lives of norethindrone and ethinyl estradiol following
administration of 1 mg NA/10 mcg EE tablets are approximately 13 hours and 24
hours, respectively.
Special Populations
Pediatric
Norethindrone acetate and ethinyl estradiol is not
indicated in children.
Geriatrics
The pharmacokinetics of norethindrone acetate and ethinyl
estradiol have not been studied in a geriatric population.
Race
The effect of race on the pharmacokinetics of norethindrone
acetate and ethinyl estradiol has not been studied.
Patients with Renal Insufficiency
The effect of renal disease on the disposition of
norethindrone acetate and ethinyl estradiol has not been evaluated. In
premenopausal women with chronic renal failure undergoing peritoneal dialysis
who received multiple doses of an oral contraceptive containing ethinyl
estradiol and norethindrone, plasma ethinyl estradiol concentrations were
higher and norethindrone concentrations were unchanged compared to concentrations
in premenopausal women with normal renal function (see PRECAUTIONS, Fluid
Retention).
Patients with Hepatic Impairment
The effect of hepatic disease on the disposition of
norethindrone acetate and ethinyl estradiol has not been evaluated. However,
ethinyl estradiol and norethindrone may be poorly metabolized in patients with
impaired liver function (see PRECAUTIONS).
Drug Interactions
See PRECAUTIONS: DRUG INTERACTIONS.
In vitro and in vivo studies have shown that estrogens
are metabolized partially by cytochrome P450 3A4 (CYP3A4). Therefore, inducers
or inhibitors of CYP3A4 may affect estrogen drug metabolism. Inducers of CYP3A4
such as St. John's Wort preparations (Hypericum perforatum), phenobarbital, carbamazepine,
and rifampin may reduce plasma concentrations of estrogens, possibly resulting
in a decrease in therapeutic effects and/or changes in the uterine bleeding
profile. Inhibitors of CYP3A4 such as erythromycin, clarithromycin,
ketoconazole, itraconazole, ritonavir and grapefruit juice may increase plasma
concentrations of estrogens and may result in side effects.
Clinical Studies
Effects on Vasomotor Symptoms
A 12-week placebo-controlled, multicenter, randomized
clinical trial was conducted in 266 symptomatic women who had at least 56 moderate
to severe hot flushes during the week prior to randomization. On average,
patients had 12 hot flushes per day upon study entry.
A total of 66 women were randomized to receive
norethindrone acetate and ethinyl estradiol 1/5, 67 women were randomized to
receive norethindrone acetate and ethinyl estradiol 0.5/2.5 and 66 women were
randomized to the placebo group. Norethindrone acetate and ethinyl estradiol
1/5 and norethindrone acetate and ethinyl estradiol 0.5/2.5 were shown to be
statistically better than placebo at weeks 4 and 12 for relief of the frequency
of moderate to severe vasomotor symptoms. See Table 2. In Table 3,
norethindrone acetate and ethinyl estradiol 1/5 was shown to be statistically
better than placebo at weeks 4 and 12 for relief of the severity of moderate to
severe vasomotor symptoms; norethindrone acetate and ethinyl estradiol 0.5/2.5
was shown to be statistically better than placebo at weeks 5 and 12 for relief
of the severity of moderate to severe vasomotor symptoms.
Table 2: Mean Change from Baseline in the Number of Moderate
to Severe Vas omotor Symptoms per Week-ITT Population, LOCF
Visit |
Placebo
(N=66) |
Norethindrone Acetate and Ethinyl Estradiol 0.5/2.5
(N=67) |
Norethindrone Acetate and Ethinyl Estradiol 1/5
(N=66) |
Baseline1 |
Mean (SD) |
76.5 (21.4) |
77.6 (26.5) |
70.0 (16.6) |
Week 4 |
Mean (SD) |
39.4 (27.6) |
30.2 (26.1) |
20.4 (22.7) |
Mean Change from Baseline (SD) |
-37.0 (26.6) |
-47.4* (26.1) |
-49.6* (22.1) |
p-Value vs. Placebo (95% CI) 2 |
|
0.041 (-20.0, -1.0) |
< 0.001 (-22.0,-6.0) |
Week 12 |
Mean (SD) |
31.1 (27.0) |
13.8 (20.4) |
11.3 (18.9) |
Mean Change from Baseline (SD) |
-45.3 (30.2) |
-63.8* (27.5) |
-58.7* (23.1) |
p-Value vs. Placebo (95%CI)2 |
|
< 0.001 (-27.0, -7.0) |
< 0.001 (-25.0, -5.0) |
*Denotes statistical significance at the 0.05 level
1 The baseline number of moderate to severe vasomotor symptoms
(MSVS) is the weekly average number of MSVS during the two week
prerandomization observation period.
2 ANCOVA - Analysis of Covariance model where the observation
variable is change from baseline; independent variables include treatment,
center and baseline as covariate. The 95% CI-Mann-Whitney confidence interval
for the difference between means (not stratified by center).
 ITT = intent to treat; LOCF = last observation carried forward; CI =
confidence interval
 2 randomized subjects (1 in Placebo and 1 in norethindrone acetate and ethinyl
estradiol) did not return diaries. |
Table 3: Mean Change from Baseline in the Daily
Severity Score of Moderate to Severe Vasomotor Symptoms per Week-ITT
Population, LOCF
Visit |
Placebo
(N=66) |
Norethindrone Acetate and
Ethinyl
Estradiol 0.5/2.5
(N=67) |
Norethindrone Acetate and
Ethinyl
Estradiol
1/5
(N=66) |
Baseline1 |
Mean (SD) |
2.49 (0.26) |
2.48 (0.22) |
2.47 (0.23) |
Week 4 |
Mean (SD) |
2.13 (0.74) |
1.88 (0.89) |
1.45 (1.03) |
Mean Change from Baseline (SD) |
-0.36 (0.68) |
-0.59 (0.83) |
-1.02* (1.06) |
p-Value vs. Placebo (95% CI)2 |
- |
0.130 (-0.3, 0.0) |
< 0.001 (-0.9, - 0.2) |
Week 5 |
Mean (SD) |
2.06 (0.79) |
1.68 (0.99) |
1.23 (1.03) |
Mean Change from Baseline (SD) |
-0.44 (0.74) |
-0.80* (0.94) |
-1.24* (1.07) |
p-Value vs. Placebo (95% CI)2 |
|
0.041 (-0.4, -0.0) |
< 0.001 (-1.2, -0.3) |
Week 12 |
Mean (SD) |
1.82 (1.03) |
1.22 (1.11) |
1.02 (1.16) |
Mean Change from Baseline (SD) |
-0.67 (1.02) |
-1.26* (1.08) |
-1.45* (1.19) |
p-Value vs. Placebo (95% CI)2 |
|
0.002 (-0.9, -0.2) |
< 0.001 (-1.4, -0.3) |
*Denotes statistical significance at the 0.05 level
1 The baseline severity of moderate to severe vasomotor symptoms
(MSVS) is the daily severity score of MSVS during the two week prerandomization
observation period.
2 ANCOVA - Analysis of Covariance model where the observation
variable is change from baseline; independent variables include treatment,
center and baseline as covariate. The 95% CI- Mann-Whitney confidence interval
for the difference between means (not stratified by center).
ITT = intent to treat; LOCF = last observation carried forward; CI = confidence
interval
2 randomized subjects (1 in Placebo and 1 in norethindrone acetate and ethinyl
estradiol) did not return diaries. |
Endometrial Hyperplasia
A 2-year, placebo-controlled, multicenter, randomized
clinical trial was conducted to determine the safety and efficacy of norethindrone
acetate and ethinyl estradiol on maintaining bone mineral density, protecting
the endometrium, and to determine effects on lipids. A total of 1265 women were
enrolled and randomized to either placebo, 0.2 mg NA/1 mcg EE, norethindrone
acetate and ethinyl estradiol 0.5/2.5, norethindrone acetate and ethinyl
estradiol 1/5 and 1 mg NA/10 mcg EE or matching unopposed EE doses (1, 2.5, 5,
or 10 mcg) for a total of 9 treatment groups. All participants received 1000 mg
of calcium supplementation daily. Of the 1265 women randomized to the various
treatment arms of this study, 137 were randomized to placebo, 146 to
norethindrone acetate and ethinyl estradiol 1/5, 136 to norethindrone acetate
and ethinyl estradiol 0.5/2.5 and 141 to EE 5 mcg and 137 to EE 2.5 mcg. Of
these, 134 placebo, 143 norethindrone acetate and ethinyl estradiol 1/5, 136
norethindrone acetate and ethinyl estradiol 0.5/2.5, 139 EE 5 mcg and 137 EE
2.5 mcg had a baseline endometrial result. Baseline biopsies were classified as
normal (in approximately 95% of subjects), or insufficient tissue (in
approximately 5% of subjects). Follow-up biopsies were obtained in
approximately 70-80% of patients in each arm after 12 and 24 months of therapy.
Results are shown in Table 4.
Table 4: Endometrial Biops y Res ults After 12 and 24
Months of Treatment (CHART Study, 376-359)
Endometrial Status |
Placebo |
Norethindrone Acetate and Ethinyl Estradiol |
EE Alone |
0.5/2.5 |
1/5 |
2.5 mcg |
5 mcg |
Number of Patients Biopsied at Baseline |
N= 134 |
N=136 |
N= 143 |
N=137 |
N=139 |
MONTH 12 (% Patients) |
Patients Biopsied (%) |
113 (84) |
103 (74) |
110 (77) |
100 (73) |
114 (82) |
Insufficient Tissue |
30 |
34 |
45 |
20 |
20 |
Atrophic Tissue |
60 |
41 |
41 |
15 |
2 |
Proliferative Tissue |
23 |
28 |
24 |
65 |
91 |
Endometrial Hyperplasia* |
0 |
0 |
0 |
0 |
1 |
MONTH 24 (%Patients) |
Patients Biopsied (%) |
94 (70) |
99 (73) |
102 (71) |
89 (65) |
107 (77) |
Insufficient Tissue |
35 |
42 |
37 |
23 |
17 |
Atrophic Tissue |
38 |
30 |
33 |
6 |
2 |
Proliferative Tissue |
20 |
27 |
32 |
60 |
86 |
Endometrial Hyperplasia* |
1 |
0 |
0 |
0 |
2 |
* All patients with endometrial hyperplasia were carried
forward for all time  Points |
Irregular Bleeding/Spotting
The cumulative incidence of amenorrhea, defined as no
bleeding or spotting obtained from subject recall, was evaluated over 12 months
for norethindrone acetate and ethinyl estradiol 0.5/2.5, norethindrone acetate
and ethinyl estradiol 1/5 and placebo arms. Results are shown in Figure 2.
Figure 2: Patients With Cumulative Amenorrhea Over
Time: Intent-to-Treat Population, Last Observation Carried Forward
Effect on Bone Mineral Density
In the 2 year study, trabecular bone mineral density
(BMD) was assessed at lumbar spine using quantitative computed tomography. A
total of 419 postmenopausal primarily Caucasian women, aged 40 to 64 years,
with intact uteri and non-osteoporotic bone mineral densities were randomized
(1:1:1) to norethindrone acetate and ethinyl estradiol 1/5, norethindrone
acetate and ethinyl estradiol 0.5/2.5 or placebo. Approximately 75% of the
subjects in each group completed the two-year study. All patients received 1000
mg calcium in divided doses. Vitamin D was not supplemented.
As shown in Figure 3, women treated with norethindrone
acetate and ethinyl estradiol 1/5 had an average increase of 3.1% in lumbar
spine BMD from baseline to Month 24. Women treated with norethindrone acetate
and ethinyl estradiol 0.5/2.5 and placebo had average decreases of –0.8% and
–6.3%, respectively, in spinal BMD from baseline to Month 24. The differences
in the changes from baseline to Month 24 in the two norethindrone acetate and
ethinyl estradiol groups compared with the placebo group were statistically
significant.
It should be noted that when measured by QCT, BMD gains
and losses are greater than when measured by dual X-ray absorptiometry (DXA).
Therefore, the differences in the changes in BMD between the placebo and active
drug treated groups will be larger when measured by QCT compared with DXA. Changes
in BMD measured by DXA should not be compared with changes in BMD measured by
QCT.
Figure 3: Mean Percent Change (+ SE) From Baseline
in Volumetric Bone Mineral Density* at Lumbar Spine Measured by Quantitative
Computed Tomography after 12 and 24 Months of Treatment (Intent-to- Treat
Population)
*It should be noted that when measured by QCT, BMD gains
and losses are greater than when measured by dual X-ray absorptiometry (DXA).
Therefore, the differences in the changes in BMD between the placebo and active
drug treated groups will be larger when measured by QCT compared with DXA. Changes
in BMD measured by DXA should not be compared with changes in BMD measured by
QCT.
Women's Health Initiative Studies
The Women's Health Initiative (WHI) enrolled a total of
27,000 predominantly healthy postmenopausal women to assess the risks and
benefits of either the use of oral 0.625 mg conjugated estrogens (CE) per day
alone or the use of oral 0.625 mg conjugated estrogens plus 2.5 mg
medroxyprogesterone acetate (MPA) per day compared to placebo in the prevention
of certain chronic diseases. The primary endpoint was the incidence of coronary
heart disease (CHD) (nonfatal myocardial infarction and CHD death), with
invasive breast cancer as the primary adverse outcome studied. A “global index”
included the earliest occurrence of CHD, invasive breast cancer, stroke,
pulmonary embolism (PE), endometrial cancer, colorectal cancer, hip fracture,
or death due to other cause. The study did not evaluate the effects of CE or
CE/MPA on menopausal symptoms.
The CE/MPA substudy was stopped early because, according
to the predefined stopping rule, the increased risk of breast cancer and
cardiovascular events exceeded the specified benefits included in the “global
index.” Results of the CE/MPA substudy, which included 16,608 women (average
age of 63 years, range 50 to 79; 83.9% White, 6.5% Black, 5.5% Hispanic), after
an average follow-up of 5.2 years are presented in Table 5 below:
Table 5: RELATIVE AND ABSOLUTE RISK SEEN IN THE Â CE/MPA
SUBSTUDY OF WHI*
Eventt |
Relative Risk CE/MPA vs placebo at 5.2 Years (95% CI*) |
Placebo
n = 8102 |
CE/MPA
n = 8506 |
Absolute Risk per 10,000 Women-years |
CHD events |
1.29 (1.02-1.63) |
30 |
37 |
Non-fatal MI |
1.32 (1.02-1.72) |
23 |
30 |
CHD death |
1.18 (0.70-1.97) |
6 |
7 |
Invasive breast cancer‡ |
1.26 (1.00-1.59) |
30 |
38 |
Stroke |
1.41 (1.07-1.85) |
21 |
29 |
Pulmonary embolism |
2.13 (1.39-3.25) |
8 |
16 |
Colorectal cancer |
0.63 (0.43-0.92) |
16 |
10 |
Endometrial cancer |
0.83 (0.47-1.47) |
6 |
5 |
Hip fracture |
0.66 (0.45-0.98) |
15 |
10 |
Death due to causes other than the events above |
0.92 (0.74-1.14) |
40 |
37 |
Global Index† |
1.15 (1.03-1.28) |
151 |
170 |
Deep vein thrombosis§ |
2.07 (1.49-2.87) |
13 |
26 |
Vertebral fractures§ |
0.66 (0.44-0.98) |
15 |
9 |
Other osteoporotic fractures§ |
0.77 (0.69-0.86) |
170 |
131 |
*nominal confidence intervals unadjusted for multiple
looks and multiple comparisons
*adapted from JAMA, 2002; 288:321-333
†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
‡includes metastatic and non-metastatic breast cancer with the exception of in
situ breast cancer
§not included in Global Index |
For those outcomes included in the “global
index,” the absolute excess risks per 10,000 women-years in the group
treated with CE/MPA were 7 more CHD events, 8 more strokes, 8 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. The
absolute excess risk of events included in the “global index” was 19 per 10,000
women-years. There was no difference between the groups in terms of allcause mortality.
(See BOXED WARNING, WARNINGS, and PRECAUTIONS.)
Women's Health Initiative Memory Study
The Women's Health Initiative Memory Study (WHIMS), a
substudy of WHI, enrolled 4,532 predominantly healthy postmenopausal women 65
years of age and older (47% were age 65 to 69 years, 35% were 70 to 74 years,
and 18% were 75 years of age and older) to evaluate the effects of CE/MPA (0.625
mg conjugated estrogens plus 2.5 mg medroxyprogesterone acetate) on the
incidence of probable dementia (primary outcome) compared with placebo.
After an average follow-up of 4 years, 40 women in the
estrogen/progestin group (45 per 10,000 women-years) and 21 in the placebo
group (22 per 10,000 women-years) were diagnosed with probable dementia. The
relative risk of probable dementia in the hormone therapy group was 2.05 (95%
CI, 1.21 to 3.48) compared to placebo. Differences between groups became
apparent in the first year of treatment. It is unknown whether these findings
apply to younger postmenopausal women. (See BOXED WARNING and WARNINGS,
Dementia.)