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 has 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, hypercho-lesterolemia, 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 (WHI) study, an increase in the number of
myocardial infarctions and strokes has been observed in women receiving CE compared
to placebo. These observations are preliminary. (See CLINICAL PHARMACOLOGY,
Clinical Studies.)
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 women-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 (0.625mg/2.5mg 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
the 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 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 (WHI) study, an increase in VTE has been observed
in women receiving CE compared to placebo. These observations are preliminary.
(See CLINICAL PHARMACOLOGY, Clinical Studies.)
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 women-years
in the CE/MPA group compared to 16 per 10,000 women-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 use of estrogens for less than one 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 to 15 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 hormone 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 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 women-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 women-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 women-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 healthcare 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 women-years, and the absolute
excess risk for CE/MPA was 23 cases per 10,000 women-years. It is unknown whether
these findings apply to younger postmenopausal women. (See CLINICAL PHARMACOLOGY,
Clinical Studies and PRECAUTIONS, Geriatric
Use.) It is unknown whether these findings apply to estrogen alone therapy.
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
Estrogen administration may lead to severe hypercalcemia in patients with breast cancer and bone metastases. If hypercalcemia occurs, use of 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 propto-sis, diplopia, or migraine. If examination reveals papilledema or retinal vascular lesions, estrogens should be permanently discontinued.