WARNINGS
See BOXED WARNINGS.
The use of unopposed estrogens in women who have a uterus is associated with
an increased risk of endometrial cancer.
Cardiovascular disorders
Estrogen and estrogen/progestin therapy have been associated with an increased
risk of cardiovascular events such as myocardial infarction and stroke, as well
as venous thrombosis and pulmonary embolism (venous thromboembolism or VTE).
Should any of these occur or be suspected, estrogens should be discontinued
immediately.
Risk factors for arterial vascular disease (e.g. hypertension, diabetes mellitus,
tobacco use, hypercholesterolemia, and obesity) and/or venous thromboembolism
(e.g., personal history or family history of VTE, obesity, and systemic lupus
erythematosus) should be managed appropriately.
Coronary heart disease and stroke
In the Women's Health Initiative study (WHI), an increase in the number of
myocardial infarctions and strokes has been observed in women receiving CE compared
to placebo.
In the CE/MPA substudy of WHI an increased risk of coronary heart disease (CHD)
events (defined as non-fatal myocardial infarction and CHD death) was observed
in women receiving CE/MPA compared to women receiving placebo (37 vs 30 per
10,000 women years). The increase in risk was observed in year one and persisted.
In the same substudy of WHI, an increased risk of stroke was observed in women
receiving CE/MPA compared to women receiving placebo (29 vs 21 per 10,000 woman-years).
The increase in risk was observed after the first year and persisted.
In postmenopausal women with documented heart disease (n = 2,763, average age
66.7 years) a controlled clinical trial of secondary prevention of cardiovascular
disease (Heart and Estrogen/Progestin Replacement Study; HERS) treatment with
CE/MPA-0.625 mg/ 2.5 mg per day demonstrated no cardiovascular benefit. During
an average follow-up of 4.1 years, treatment with CE/MPA did not reduce the
overall rate of CHD events in postmenopausal women with established coronary
heart disease. There were more CHD events in the CE/MPA-treated group than in
placebo group in year 1, but not during the subsequent years. Two thousand three
hundred and twenty one women from the original HERS trial agreed to participate
in an open label extension of HERS, HERS II. Average follow-up in HERS II was
an additional 2.7 years, for a total of 6.8 years overall. Rates of CHD events
were comparable among women in the CE/MPA group and in the placebo group in
HERS, HERS II, and overall.
Large doses of estrogen (5 mg conjugated estrogens per day), comparable to
those used to treat cancer of the prostate and breast, have been shown in a
large prospective clinical trial in men to increase the risks of nonfatal myocardial
infarction, pulmonary embolism, and thrombophlebitis.
Venous thromboembolism (VTE)
In the Women's Health Initiative study (WHI), an increase in VTE has been observed
in women receiving CE compared to placebo. In the CE/MPA substudy of WHI, a
2-fold greater rate of VTE, including deep venous thrombosis and pulmonary embolism,
was observed in women receiving CE/MPA compared to women receiving placebo.
The rate of VTE was 34 per 10,000 woman-years in the CE/MPA group compared to
16 per 10,000 woman-years in the placebo group. The increase in VTE risk was
observed during the first year and persisted.
If feasible, estrogens should be discontinued at least 4 to 6 weeks before
surgery of the type associated with an increased risk of thromboembolism, or
during periods of prolonged immobilization.
Malignant Neoplasms
Endometrial cancer
The use of unopposed estrogens in women with intact uteri has been associated
with an increased risk of endometrial cancer. The reported endometrial cancer
risk among unopposed estrogen users is about 2- to 12-fold greater than in non-users
and appears dependent on duration of treatment and on estrogen dose. Most studies
show no significant increased risk associated with the use of estrogens for
less than 1 year. The greatest risk appears associated with prolonged use with
increased risks of 15- to 24-fold for five to ten years or more, and this risk
has been shown to persist for at least 8 to15 years after estrogen therapy is
discontinued.
Clinical surveillance of all women taking estrogen/progestin combinations is
important. Adequate diagnostic measures, including endometrial sampling when
indicated, should be undertaken to rule out malignancy in all cases of undiagnosed
persistent or recurring abnormal vaginal bleeding. There is no evidence that
the use of natural estrogens results in a different endometrial risk profile
than synthetic estrogens of equivalent estrogen dose. Adding a progestin to
estrogen therapy has been shown to reduce the risk of endometrial hyperplasia,
which may be a precursor to endometrial cancer.
Breast cancer
The use of estrogens and progestins by postmenopausal women has been reported
to increase the risk of breast cancer. The most important randomized clinical
trial providing information about this issue is the Women's Health Initiative
(WHI) substudy of CE/MPA (see CLINICAL PHARMACOLOGY, Clinical
Studies). The results from observational studies are generally consistent
with those of the WHI clinical trial and report no significant variation in
the risk of breast cancer among different estrogens or progestins, doses, or
routes of administration.
The CE/MPA substudy of WHI reported an increased risk of breast cancer in women
who took CE/MPA for a mean follow-up of 5.6 years. Observational studies have
also reported an increased risk for estrogen/progestin combination therapy,
and a smaller increased risk for estrogen alone therapy, after several years
of use. In the WHI trial and from observational studies, the excess risk increased
with duration of use. From observational studies, the risk appeared to return
to baseline in about five years after stopping treatment. In addition, observational
studies suggest that the risk of breast cancer was greater, and became apparent
earlier, with estrogen/progestin combination therapy as compared to estrogen
alone therapy.
In the CE/MPA substudy, 26% of the women reported prior use of estrogen alone
and/or estrogen/progestin combination hormone therapy. After a mean follow-up
of 5.6 years during the clinical trial, the overall relative risk of invasive
breast cancer was 1.24 (95% confidence interval 1.01-1.54), and the overall
absolute risk was 41 vs 33 cases per 10,000 woman-years, for CE/MPA compared
with placebo. Among women who reported prior use of hormone therapy, the relative
risk of invasive breast cancer was 1.86, and the absolute risk was 46 vs 25
cases per 10,000 woman-years, for CE/MPA compared with placebo. Among women
who reported no prior use of hormone therapy, the relative risk of invasive
breast cancer was 1.09, and the absolute risk was 40 vs 36 cases per 10,000
woman-years for CE/MPA compared with placebo. In the same substudy, invasive
breast cancers were larger and diagnosed at a more advanced stage in the CE/MPA
group compared with the placebo group. Metastatic disease was rare with no apparent
difference between the two groups. Other prognostic factors such as histologic
subtype, grade and hormone receptor status did not differ between the groups.
The use of estrogen plus progestin has been reported to result in an increase
in abnormal mammograms requiring further evaluation. All women should receive
yearly breast examinations by a health care provider and perform monthly breast
self-examinations. In addition, mammography examinations should be scheduled
based on patient age, risk factors, and prior mammogram results.
Dementia
In the Women's Health Initiative Memory Study (WHIMS), 4,532 generally healthy
postmenopausal women 65 years of age and older were studied, of whom 35% were
70 to 74 years of age and 18% were 75 or older. After an average follow-up of
4 years, 40 women being treated with CE/MPA (1.8%, n = 2,229) and 21 women in
the placebo group (0.9%, n = 2,303) received diagnoses of probable dementia.
The relative risk for CE/MPA versus placebo was 2.05 (95% confidence interval
1.21 – 3.48), and was similar for women with and without histories of menopausal
hormone use before WHIMS. The absolute risk of probable dementia for CE/MPA
versus placebo was 45 versus 22 cases per 10,000 woman-years, and the absolute
excess risk for CE/MPA was 23 cases per 10,000 woman-years. It is unknown whether
these findings apply to younger postmenopausal women. (See CLINICAL PHARMACOLOGY,
Clinical Studies and PRECAUTIONS, Geriatric
Use.)
Gallbladder Disease
A 2- to 4-fold increase in the risk of gallbladder disease requiring surgery
in postmenopausal women receiving estrogens has been reported.
Hypercalcemia
Administration of estrogen may lead to severe hypercalcemia in patients with
breast cancer and bone metastases. If this occurs, the drug should be stopped
and appropriate measures taken to reduce the serum calcium level.
Visual abnormalities
Retinal vascular thrombosis has been reported in patients receiving estrogens.
Discontinue medication pending examination if there is sudden partial or complete
loss of vision, or a sudden onset of proptosis, diplopia, or migraine. If examination
reveals papilledema or retinal vascular lesions, estrogens should be permanently
discontinued.