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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.
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, and central nervous system. Progestins produce similar endometrial changes to those of the naturally occurring hormone progesterone.
Estradiol is well absorbed through the gastrointestinal tract. Following oral administration of estradiol and norethindrone acetate tablets, peak plasma estradiol concentrations are reached slowly within 5 to 8 hours. When given orally, estradiol is extensively metabolized (first-pass effect) to estrone sulfate, with smaller amounts of other conjugated and unconjugated estrogens. After oral administration, norethindrone acetate is rapidly absorbed and transformed to norethindrone. It undergoes first-pass metabolism in the liver and other enteric organs, and reaches a peak plasma concentration within 0.5 to 1.5 hours after the administration of estradiol and norethindrone acetate tablets. The oral bioavailability of estradiol and norethindrone following administration of estradiol and norethindrone acetate 1 mg/0.5 mg when compared to a combination oral solution is 53% and 100%, respectively. Administration of estradiol and norethindrone acetate 1 mg/0.5 mg with food did not modify the bioavailability of estradiol, although increases in AUC0-72 of 19% and decreases in Cmax of 36% for norethindrone were seen.
The pharmacokinetic parameters of estradiol (E2), estrone (E1), and norethindrone (NET) following oral administration of 1 estradiol and norethindrone acetate 1 mg/0.5 mg or 2 estradiol and norethindrone acetate 0.5 mg/0.1 mg tablet(s) to healthy postmenopausal women are summarized in Table 1.
TABLE 1: PHARMACOKINETIC PARAMETERS AFTER ADMINISTRATION
OF 1 TABLET OF ESTRADIOL AND NORETHINDRONE ACETATE 1 MG/0.5 MG OR 2 TABLETS OF
ESTRADIOL AND NORETHINDRONE ACETATE 0.5 MG/0.1 MG TO HEALTHY POSTMENOPAUSAL
|1 x Estradiol and Norethindrone Acetate 1 mg/0.5 mg
|2 x Estradiol and Norethindrone Acetate 0.5 mg/0.1 mg
|AUC0-t (pg/mL*h)||766.5 (48)||697.3 (53)|
|Cmax (pg/mL)||26.8 (36)||26.5 (37)|
|tmax (h): median (range)||6.0 (0.5-16.0)||6.5 (0.5-16.0)|
|AUC0-t (pg/mL*h)||4469.1 (48)||4506.4 (44)|
|Cmax (pg/mL)||195.5 (37)||199.5 (30)|
|tmax (h): median (range)||6.02 (1.0-9.0)||6.0 (2.0-9.0)|
|t½ (h)§||10.7 (44)Þ||11.8 (25)Þ|
|AUC0-t (pg/mL*h)||21043 (41)||8407 (43)|
|Cmax (pg/mL)||5249.5 (47)||2375.4 (41)|
|tmax (h) : median (range)||0.7 (0.7-1.25)||0.8 (0.7-1.3)|
|t½ (h)||9.8 (32)β||11.4 (36)a|
|AUC = area under the curve, 0 – last quantifiable sample,
C = maximum plasma concentration, t = time at maximum plasma concentration, t ½
* geometric mean
†geometric % coefficient of variation
‡baseline unadjusted data
§baseline unadjusted data
Following continuous dosing with once-daily administration of estradiol and norethindrone acetate 1 mg/0.5 mg, serum levels of estradiol, estrone, and norethindrone reached steady-state within two weeks with an accumulation of 33 to 47% above levels following single dose administration. Unadjusted circulating levels of E2, E1, and NET during estradiol and norethindrone acetate 1 mg/0.5 mg treatment at steady-state (dosing at time 0) are provided in Figures 1a and 1b.
Figure 1a: Levels of Estradiol and Estrone at
Steady-State During Continuous Dosing with Estradiol and Norethindrone Acetate
1 mg /0.5 mg (n=24 )
Figure 1b : Levels of Norethindrone at Steady-State
During Continuous Dosing with Estradiol and Norethindrone Acetate 1 mg /0.5 mg
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. Estradiol circulates in the blood bound to sex-hormone-binding globulin (SHBG) (37%) and to albumin (61%), while only approximately 1 to 2% is unbound. Norethindrone also binds to a similar extent to SHBG (36%) and to albumin (61%).
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 intestine 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.
The most important metabolites of norethindrone are isomers of 5α- dihydro-norethindrone and tetrahydro-norethindrone, which are excreted mainly in the urine as sulfate or glucuronide conjugates.
Estradiol, estrone, and estriol are excreted in the urine along with glucuronide and sulfate conjugates. The half-life of estradiol following single dose administration of estradiol and norethindrone acetate 1 mg/0.5 mg is 12 to 14 hours. The terminal half-life of norethindrone is about 8 to11 hours.
No pharmacokinetic studies were conducted in special populations, including patients with renal or hepatic impairment.
Co-administration of estradiol with norethindrone acetate did not elicit any apparent influence on the pharmacokinetics of norethindrone. Similarly, no relevant interaction of norethindrone on the pharmacokinetics of estradiol was found within the NETA dose range investigated in a single dose study.
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 result in side effects.
Effects On Vasomotor Symptoms
In a 12-week randomized clinical trial involving 92 subjects, estradiol and norethindrone acetate 1 mg/0.5 mg was compared to 1 mg of estradiol and to placebo. The mean number and intensity of hot flushes were significantly reduced from baseline to week 4 and 12 in both the estradiol and norethindrone acetate 1 mg/0.5 mg and the 1 mg estradiol group compared to placebo (see Figure 2).
Figure 2 : Mean Weekly Number of Moderate and Severe
Hot Flushes in a 12-Week Study
In a study conducted in Europe a total of 577 postmenopausal women were randomly assigned to either estradiol and norethindrone acetate 0.5 mg/0.1 mg, 0.5 mg E2/0.25 mg NETA, or placebo for 24 weeks of treatment. The mean number and severity of hot flushes were significantly reduced at week 4 and week 12 in the estradiol and norethindrone acetate 0.5 mg/0.1 mg (see Figure 3) and 0.5 mg E2/0.25 mg NETA groups compared to placebo.
Figure 3: Mean Number of Moderate to Severe Hot Flushes
for Weeks 0 Through 12
Effects On The Endometrium
Estradiol and norethindrone acetate 1 mg/0.5 mg reduced the incidence of estrogen-induced endometrial hyperplasia at 1 year in a randomized, controlled clinical trial. This trial enrolled 1,176 subjects who were randomized to one of 4 arms: 1 mg estradiol unopposed (n=296), 1 mg E2 + 0.1 mg NETA (n=294), 1 mg E2+ 0.25 mg NETA (n=291), and estradiol and norethindrone acetate 1 mg/0.5 mg (n=295). At the end of the study, endometrial biopsy results were available for 988 subjects. The results of the 1 mg estradiol unopposed arm compared to estradiol and norethindrone acetate 1 mg/0.5 mg are shown in Table 2.
TABLE 2 : INCIDENCE OF ENDOMETRIAL HYPERPLASIA WITH
UNOPPOSED ESTRADIOL AND ESTRADIOL AND NORETHINDRONE ACETATE 1 MG/0.5 MG IN A
12- MONTH STUDY
|1 mg E2
|Estradiol and Norethindrone Acetate 1 mg E2/0.50mg NETA
|1 mg E2/0.25 mg NETA
|1 mg E2/0.1 mg NETA
|No. of subjects with histological evaluation at the end of the study||247||241||251||249|
|No. (%) of subjects with endometrial hyperplasia at the end of the study||36 (14.6%)||1 (0.4%)||1 (0.4%)||2 (0.8%)|
Effects On Uterine Bleeding Or Spotting
During the initial months of therapy, irregular bleeding or spotting occurred with estradiol and norethindrone acetate 1 mg/0.5 mg treatment. However, bleeding tended to decrease over time, and after 12 months of treatment with estradiol and norethindrone acetate 1 mg/0.5 mg, about 86% of women were amenorrheic (see Figure 4).
Figure 4 : Patients Treated with Estradiol and
Norethindrone Acetate 1 mg /0.5 mg with Cumulative Amenorrhea over Time
Percentage of Women with no Bleeding or Spotting at any Cycle Through Cycle 13 Intent
to Treat Population, LOCF
Note: The percentage of patients who were amenorrheic in a given cycle and through cycle 13 is shown. If data were missing, the bleeding value from the last reported day was carried forward (LOCF).
In the clinical trial with estradiol and norethindrone acetate 0.5 mg/0.1 mg, 88% of women were amenorrheic after 6 months of treatment (See Figure 5).
Figure 5 : Patients Treated with Estradiol and
Norethindrone Acetate 0.5 mg /0.1 mg with Cumulative Amenorrhea over Time
Percentage of Women with no Bleeding or Spotting at any Cycle Through Cycle 6, Intent
to Treat Population, LOCF
Effects On Bone Mineral Density
The results of two randomized, multi-center, calcium-supplemented (500 to 1000 mg/day), placebocontrolled, 2 year clinical trials have shown that estradiol and norethindrone acetate 1 mg/0.5 mg and estradiol 0.5 mg are effective in preventing bone loss in postmenopausal women. While estradiol and norethindrone acetate 0.5 mg/0.1 mg was not directly studied in these trials, the US trial showed that addition of NETA to estradiol enhances the effect on BMD, therefore the BMD changes expected from treatment with estradiol and norethindrone acetate 0.5 mg/0.1 mg should be at least as great as observed with estradiol 0.5 mg. A total of 462 postmenopausal women with intact uteri and baseline BMD values for lumbar spine within 2 standard deviations of the mean in healthy young women were enrolled. In a US trial, 327 postmenopausal women (mean time from menopause 2.5 to 3.1 years) with a mean age of 53 years were randomized to 7 groups (0.25, 0.5 mg, and 1 mg of estradiol alone, 1 mg estradiol with 0.25 mg norethindrone acetate, 1 mg estradiol with 0.5 mg norethindrone acetate, and 2 mg estradiol with 1 mg norethindrone acetate, and placebo.) In a European trial (EU trial), 135 postmenopausal women (mean time from menopause 8.4 to 9.3 years) with a mean age of 58 years were randomized to 1 mg estradiol with 0.25 mg norethindrone acetate, 1 mg estradiol with 0.5 mg norethindrone acetate, and placebo. Approximately 58% and 67% of the randomized subjects in the two clinical trials, respectively, completed the two clinical trials. BMD was measured using dual-energy xray absorptiometry (DEXA).
A summary of the results comparing estradiol and norethindrone acetate 1 mg/0.5 mg and estradiol 0.5 mg to placebo from the two prevention trials is shown in Table 3.
TABLE 3: PERCENTAGE CHANGE (MEAN ± SD) IN BONE MINERAL
DENSITY (BMD) FOR ESTRADIOL AND NORETHINDRONE ACETATE 1 MG/0.5 MG AND 0.5 MG E2
(Intent to Treat Analys is , Last Observation Carried Forward)
|US Trial||EU Trial|
|0.5 mg E2*
|Estradiol and Norethindrone Acetate 1 mg/0.5 mg
|Estradiol and Norethindrone Acetate 1 mg/0.5 mg
|Lumbar spine||-2.1 ± 2.9||2.3 ± 2.8 †||3.8 ± 3.0†||-0.9 ± 4.0||5.4 ± 4.8†|
|Femoral neck||-2.3 ± 3.4||0.3 ± 2.9 ‡||1.8 ± 4.1†||-1.0 ± 4.6||0.7 ± 6.1|
|Femoral trochanter||-2.0 ± 4.3||1.7 ± 4.1 §||3.7 ± 4.3†||0.8 ± 6.9||6.3 ± 7.6 t|
|US = United States, EU = European
* While estradiol and norethindrone acetate 0.5 mg/0.1 mg was not directly studied in these trials, the US trial showed that addition of NETA to estradiol enhances the effect on BMD, therefore the BMD changes expected from treatment with estradiol and norethindrone acetate 0.5 mg/0.1 mg should be at least as great as observed with estradiol 0.5 mg.
†Significantly (p < 0.001) different from placebo
‡Significantly (p < 0.007) different from placebo
§Significantly (p < 0.002) different from placebo
The overall difference in mean percentage change in BMD at the lumbar spine in the US trial (1000 mg/day calcium) between estradiol and norethindrone acetate 1 mg/0.5 mg and placebo was 5.9% and between estradiol 0.5 mg and placebo was 4.4%. In the European trial (500 mg/day calcium), the overall difference in mean percentage change in BMD at the lumbar spine was 6.3%. Estradiol and norethindrone acetate 1 mg/0.5 mg and estradiol 0.5 mg also increased BMD at the femoral neck and femoral trochanter compared to placebo. The increase in lumbar spine BMD in the US and European clinical trials for estradiol and norethindrone acetate 1 mg/0.5 mg and estradiol 0.5 mg is displayed in Figure 6.
Figure 6 : Percentage Chang e in Bone Mineral Density
(BMD) ± SEM of the Lumbar Spine (L1-L4 ) for Estradiol and Norethindrone
Acetate 1 mg /0.5 mg and Estradiol 0.5 mg (Intent to Treat Analys is with Last
Observation Carried Forward)
†While estradiol and norethindrone acetate 0.5 mg/0.1 mg was not directly studied in these trials, the US trial showed that addition of NETA to estradiol enhances the effect on BMD, therefore the BMDchanges expected from treatment with estradiol and norethindrone acetate 0.5 mg/0.1 mg should be at least as great as observed with estradiol 0.5 mg.
Effect On Bone Turnover
Estradiol and norethindrone acetate 1 mg/0.5 mg reduced serum and urine markers of bone turnover with a marked decrease in bone resorption markers (e.g., urinary pyridinoline crosslinks Type 1 collagen telopeptide, pyridinoline, deoxypyridinoline) and to a lesser extent in bone formation markers (e.g., serum osteocalcin, bone-specific alkaline phosphatase, C-terminal propetide of type 1 collagen). The suppression of bone turnover markers was evident by 3 months and persisted throughout the 24-month treatment period.
Treatment with 0.5 mg estradiol decreased biochemical markers of bone resorption (urinary pyridinoline, urinary deoxypyridinoline) and bone formation (bone-specific alkaline phosphatase) compared to placebo. These decreases occurred by 6 months of treatment after which the levels were maintained throughout the 24 months.
Women's Health Initiative Studies
The WHI enrolled a total of 27,000 predominantly healthy postmenopausal women in two sub-studies to assess the risks and benefits of either the use of oral conjugated estrogens (CE 0.625 mg per day) alone or the use of oral conjugated estrogens (CE 0.625 mg) plus medroxyprogesterone acetate (MPA 2.5 mg 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 (MI), silent MI 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 estrogen-plus-progestin sub-study was stopped early. According to the predefined stopping rule, after an average follow-up of 5.2 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 included in the “global index” was 19 per 10,000 women-years (RR 1.15, 95% nCI 1.03-1.28).
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/MPA were six more CHD events, seven more strokes, ten more PEs, and eight more invasive breast cancers, while the absolute risk reductions per 10,000 women-years were seven fewer colorectal cancers and five fewer hip fractures. (See BOXED WARNINGS, WARNINGS, and PRECAUTIONS.)
Results of the estrogen-plus-progestin sub-study, which included 16,608 women (average age of 63 years, range 50 to 79; 83.9% White, 6.8% Black, 5.4% Hispanic, 3.9% Other) are presented in Table 4 below:
TABLE 4 : RELATIVE AND ABSOLUTE RISK SEEN IN THE
ESTROGEN-PLUS-PROGESTIN SUB-STUDY OF WHI AT AN AVERAGE OF 5.6 YEARS*
|Event||Relative Risk CE/MPA vs. Placebo (95% nCI†)||CE/MPA
n = 8,506
n = 8,102
|Absolute Risk per 10,000 Women-Years|
|CHD events||1.24 (1.00-1.54)||39||33|
|Non-fatal MI||1.28 (1.00-1.63)||31||25|
|CHD death||1.10 (0.70-1.75)||8||8|
|All strokes||1.31 (1.02-1.68)||31||24|
|Ischemic stroke||1.44 (1.09-1.90)||26||18|
|Deep vein thrombosis||1.95 (1.43-2.67)||26||13|
|Pulmonary embolism||2.13 (1.45-3.11)||18||8|
|Invasive breast cancer‡||1.24 (1.01-1.54)||41||33|
|Invasive colorectal cancer||0.56 (0.38-0.81)||9||16|
|Endometrial cancer||0.81 (0.48-1.36)||6||7|
|Cervical cancer||1.44 (0.47-4.42)||2||1|
|Hip fracture||0.67 (0.47-0.96)||11||16|
|Vertebral fractures||0.65 (0.46-0.92)||11||17|
|Lower arm/wrist fractures||0.71 (0.59-0.85)||44||62|
|Total fractures||0.76 (0.69-0.83)||152||199|
|*Results are based on centrally adjudicated data.
Mortality data was not part of the adjudicated data; however, data at 5.2 years
of follow-up showed no difference between the groups in terms of all-cause mortality
(RR 0.98, 95% nCI 0.82-1.18).
†Nominal confidence intervals unadjusted for multiple looks and multiple comparisons.
‡Includes metastatic and non-metastatic breast cancer, with the exception of in situ breast cancer.
The estrogen-alone sub-study was also stopped early because an increased risk of stroke was observed, and it was deemed that no further information would be obtained regarding the risks and benefits of estrogen alone in predetermined primary endpoints. Results of the estrogen-alone sub-study, which included 10,739 women (average age of 63 years, range 50 to 79; 75.3% White, 15.1% Black, 6.1% Hispanic, 3.6% Other), after an average follow-up of 6.8 years are presented in Table 5 below.
TABLE 5 : RELATIVE AND ABSOLUTE RISK SEEN IN THE
ESTROGEN-ALONE SUB-STUDY OF WHI*
|Event||Relative Risk CE vs.Placebo (95% nCI* )||CE
n = 5,310
n = 5,429
|Absolute Risk per 10,000 Women-Years|
|CHD events† Non-fatal MI† CHD death†||0.95 (0.79-1.16)||53||56|
|Deep vein thrombosis†,§||1.47 (1.062.06)||23||15|
|Pulmonary embolism‡||1.37 (0.90-2.07)||14||10|
|Invasive breast cancer‡||0.80 (0.621.04)||28||34|
|Colorectal cancer‡||1.08 (0.751.55)||17||16|
|Hip fracture‡||0.61 (0.410.91)||11||17|
|Vertebral fractures‡,§||0.62 (0.420.93)||11||17|
|Total fractures‡,§||0.70 (0.630.79)||139||195|
|Death due to other causes‡,¶||1.08 (0.881.32)||53||50|
|Overall mortality‡,§||1.04 (0.881.22)||81||78|
|Global Index‡,#||1.01 (0.911.12)||192||190|
|*Nominal confidence intervals unadjusted for multiple
looks and multiple comparisons.
†Results are based on centrally adjudicated data for an average followup of 7.1 years.
‡Results are based on an average follow-up of 6.8 years.
§Not included in Global Index.
¶All deaths, except from breast or colorectal cancer, definite/probable CHD, PE or cerebrovascular disease.
#A subset of the events was combined in a “global index,” defined as the earliest occurrence of CHD events, invasive breast cancer, stroke, pulmonary embolism, colorectal cancer, hip fracture, or death due to other causes.
For those outcomes included in the WHI “global index” that reached statistical significance, the absolute excess risk per 10,000 women-years in the group treated with estrogen-alone was 12 more strokes, while the absolute risk reduction per 10,000 women-years was six fewer hip fractures. The absolute excess risk of events included in the “global index” was a non-significant two events per 10,000 women-years. There was no difference between the groups in terms of all-cause mortality. (See BOXED WARNINGS, WARNINGS, and PRECAUTIONS.)
Final adjudicated results for CHD events from the estrogen-alone sub-study, after an average follow-up of 7.1 years, reported no overall difference for primary CHD events (nonfatal MI, silent MI and CHD death) in women receiving CE alone compared with placebo (see TABLE 5).
Women's Health Initiative Memory Study
The estrogen plus progestin Women's Health Initiative Memory Study (WHIMS) sub-study of WHI enrolled 4,532 predominantly healthy postmenopausal women 65 years of age and older (47%, age 65 to 69 years, 35%, age 70 to 74 years, 18%, 75 years of age and older) to evaluate the effects of CE 0.625 mg plus MPA 2.5 mg daily on the incidence of probable dementia (primary outcome) compared with placebo.
After an average follow-up of four years, 40 women in the estrogen-plus-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, 1.21-3.48) compared to placebo. It is unknown whether these findings apply to younger postmenopausal women. (See BOXED WARNINGS Cardiovascular And Other Risks, WARNINGS, Dementia, and PRECAUTIONS, Geriatric use.)
The estrogen-alone WHIMS, a sub-study of the WHI study, enrolled 2,947 predominantly healthy postmenopausal women 65 years of age and older (45%, age 65 to 69 years, 36%, age 70 to 74 years, 19%, 75 years of age and older) to evaluate the effects of conjugated estrogens (CE 0.625 mg) on the incidence of probable dementia (primary outcome) compared with placebo.
After an average follow-up of 5.2 years, 28 women in the estrogen-alone group (37 per 10,000 women-years) and 19 in the placebo group (25 per 10,000 women-years) were diagnosed with probable dementia. The relative risk of probable dementia in the estrogen-alone group was 1.49 (95% CI 0.83- 2.66) compared to placebo.
When data from the two populations were pooled as planned in the WHIMS protocol, the reported overall relative risk for probable dementia was 1.76 (95% CI 1.19-2.60). Differences between groups became apparent in the first year of treatment. It is unknown whether these findings apply to younger postmenopausal women. (See BOXED WARNINGS, WARNINGS, Dementia, and PRECAUTIONS, Geriatric use.)
Last reviewed on RxList: 4/1/2014
This monograph has been modified to include the generic and brand name in many instances.
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