A. General
1. Addition of a progestin when a woman has not had a
hysterectomy
Studies of the addition of a progestin for 10 or more days of a
cycle of estrogen administration, or daily with estrogen in a continuous
regimen, have reported a lowered incidence of endometrial hyperplasia than would
be induced by estrogen treatment alone. Endometrial hyperplasia may be a
precursor to endometrial cancer.
There are, however, possible risks that may be associated with the use of
progestins with estrogens compared to estrogen-alone regimens. These include: a
possible increased risk of breast cancer, adverse effects on lipoprotein
metabolism (lowering HDL, raising LDL) and impairment of glucose
tolerance.
2. Elevated blood pressure
In a small number of case reports, substantial increases in blood
pressure have been attributed to idiosyncratic reactions to estrogens. In a
large, randomized, placebo-controlled clinical trial, a generalized effect of
estrogen therapy on blood pressure was not seen. Blood pressure should be
monitored at regular intervals during estrogen use.
3. Hypertriglyceridemia
In patients with
pre-existing hypertriglyceridemia, estrogen therapy may be associated with
elevations of plasma triglycerides leading to pancreatitis and other
complications. Consider discontinuation of treatment if pancreatitis or other
complications develop.
In the HOPE study, the mean
percent increase from baseline in serum triglycerides after one year of
treatment with PREMARIN 0.625 mg, 0.45 mg, and 0.3 mg compared with placebo were
34.3, 30.2, 25.1, and 10.7, respectively. After two years of treatment, the mean
percent changes were 47.6, 32.5, 19.0, and 5.5, respectively.
4. Impaired liver function and past history of
cholestatic jaundice
Estrogens may be poorly metabolized in patients with impaired
liver function. For patients with a history of cholestatic jaundice associated
with past estrogen use or with pregnancy, caution should be exercised, and in
the case of recurrence, medication should be discontinued.
5. Hypothyroidism
Estrogen administration leads to increased thyroid-binding
globulin (TBG) levels. Patients with normal thyroid function can compensate for
the increased TBG by making more thyroid hormone, thus maintaining free T4 and T3 serum concentrations in the
normal range. Patients dependent on thyroid hormone replacement therapy who are
also receiving estrogens may require increased doses of their thyroid
replacement therapy. These patients should have their thyroid function monitored
in order to maintain their free thyroid hormone levels in an acceptable
range.
6. Fluid retention
Estrogens may cause some degree of fluid retention. Patients with
conditions that might be influenced by this factor, such as cardiac or renal
dysfunction, warrant careful observation when estrogens are prescribed.
7. Hypocalcemia
Estrogens should be used with caution in individuals with severe
hypocalcemia.
8. Ovarian cancer
The estrogen plus progestin
substudy of WHI reported a non-statistically significant increased risk of
ovarian cancer. After an average follow-up of 5.6 years, the relative risk for
ovarian cancer for CE/MPA versus placebo was 1.58 (95 percent nCI 0.77 – 3.24).
The absolute risk for CE/MPA versus placebo was 4.2 versus 2.7 cases per
10,000 women-years. In some epidemiologic studies, the use of estrogen-only
products, in particular for 5 or more years, has been associated with an
increased risk of ovarian cancer. However, the duration of exposure associated
with increased risk is not consistent across all epidemiologic studies and some
report no association.
9. Exacerbation of endometriosis
Endometriosis may be exacerbated with administration of estrogen
therapy.
A few cases of malignant transformation of residual endometrial implants have
been reported in women treated post-hysterectomy with estrogen alone therapy.
For patients known to have residual endometriosis post-hysterectomy, the
addition of progestin should be considered.
10. Exacerbation of other conditions
Estrogen therapy may cause an exacerbation of asthma, diabetes
mellitus, epilepsy, migraine, porphyria, systemic lupus erythematosus, and
hepatic hemangiomas and should be used with caution in patients with these
conditions.
B. Patient Information
Physicians are advised to discuss the contents of the PATIENT INFORMATION leaflet with patients
for whom they prescribe PREMARIN.
C. Laboratory Tests
Serum follicle stimulating
hormone and estradiol levels have not been shown to be useful in the management
of moderate to severe vasomotor symptoms and moderate to severe symptoms of
vulvar and vaginal atrophy.
Laboratory parameters may
be useful in guiding dosage for the treatment of hypoestrogenism due to
hypogonadism, castration and primary ovarian failure.
D. Drug/Laboratory Test Interactions
- Accelerated prothrombin time, partial thromboplastin time, and platelet
aggregation time; increased platelet count; increased factors II, VII antigen,
VIII antigen, VIII coagulant activity, IX, X, XII, VII-X complex, II-VII-X
complex, and beta-thromboglobulin; decreased levels of anti-factor Xa and
antithrombin III, decreased antithrombin III activity; increased levels of
fibrinogen and fibrinogen activity; increased plasminogen antigen and activity.
- Increased thyroid binding globulin (TBG) levels leading to increased
circulating total thyroid hormone levels as measured by protein-bound iodine
(PBI), T4 levels (by column or by radioimmunoassay) or
T3 levels by radioimmunoassay. T3
resin uptake is decreased, reflecting the elevated TBG. Free T4 and free T3 concentrations are
unaltered. Patients on thyroid replacement therapy may require higher doses of
thyroid hormone.
- Other binding proteins may be elevated in serum, i.e., corticosteroid
binding globulin (CBG), sex hormone binding globulin (SHBG), leading to
increased total circulating corticosteroids and sex steroids, respectively. Free
hormone concentrations may be decreased. Other plasma proteins may be increased
(angiotensinogen/renin substrate, alpha-1-antitrypsin, ceruloplasmin).
- Increased plasma HDL and HDL2 cholesterol subfraction
concentrations, reduced LDL cholesterol concentrations, increased triglyceride
levels.
- Impaired glucose tolerance.
E. Carcinogenesis, Mutagenesis, Impairment of
Fertility
(See BOXED WARNINGS,
WARNINGS, and PRECAUTIONS.)
Long-term continuous administration of natural and synthetic estrogens in
certain animal species increases the frequency of carcinomas of the breast,
uterus, cervix, vagina, testis, and liver.
F. Pregnancy
PREMARIN should not be used during pregnancy. (See CONTRAINDICATIONS.)
G. Nursing Mothers
PREMARIN should not be used
during lactation. Estrogen administration to nursing mothers has been shown to
decrease the quantity and quality of the milk. Detectable amounts of estrogens
have been identified in the milk of mothers receiving this drug.
H. Pediatric Use
Estrogen therapy has been used for the induction of puberty in
adolescents with some forms of pubertal delay. Safety and effectiveness in
pediatric patients have not otherwise been established.
Large and repeated doses of estrogen over an extended time period have been
shown to accelerate epiphyseal closure, which could result in short stature if
treatment is initiated before the completion of physiologic puberty in normally
developing children. If estrogen is administered to patients whose bone growth
is not complete, periodic monitoring of bone maturation and effects on
epiphyseal centers is recommended during estrogen administration.
Estrogen treatment of prepubertal girls also induces premature breast
development and vaginal cornification, and may induce vaginal bleeding. In boys,
estrogen treatment may modify the normal pubertal process and induce
gynecomastia. (See INDICATIONS AND
USAGE and DOSAGE AND
ADMINISTRATION.)
I. Geriatric Use
With respect to efficacy in the approved indications, there have
not been sufficient numbers of geriatric patients involved in studies utilizing
PREMARIN to determine whether those over 65 years of age differ from younger
subjects in their response to PREMARIN.
In the estrogen alone substudy of the Women's Health Initiative (WHI) study,
46 percent (n=4,943) were 65 years of age and older, while 7.1 percent (n=767)
were 75 years of age and older. There was a higher relative risk (daily
conjugated estrogens [CE 0.625 mg] versus placebo) of stroke in women less than
75 years of age compared to women 75 years and older.
In the estrogen alone Women's Health Initiative Memory Study (WHIMS), a
substudy of WHI, a population of 2,947 hysterectomized women, 65 to 79 years of
age, was randomized to daily CE 0.625 mg or placebo. After an average follow-up
of 5.2 years, the relative risk (CE versus placebo) of probable dementia was
1.49 (95 percent CI 0.83-2.66). The absolute risk of developing probable
dementia with estrogen alone was 37 versus 25 cases per 10,000 women-years
compared with placebo.
Of the total number of subjects in the estrogen plus progestin substudy of
the Women's Health Initiative study, 44 percent (n=7,320) were 65 years of age
and older, while 6.6 percent (n=1,095) were 75 years and older. In women 75
years of age and older compared to women less than 74 years of age, there was a
higher relative risk of nonfatal stroke and invasive breast cancer in the
estrogen plus progestin group versus placebo. In women greater than 75, the
increased risk of nonfatal stroke and invasive breast cancer observed in the
estrogen plus progestin group compared to placebo was 75 versus 24 per 10,000
women-years and 52 versus 12 per 10,000 women years, respectively.
In the estrogen plus progestin substudy of WHIMS, a population of 4,532
postmenopausal women, 65 to 79 years of age, was randomized to daily CE 0.625
mg/MPA 2.5 mg or placebo. In the estrogen plus progestin group, after an average
follow-up of 4 years, the relative risk (CE/MPA versus placebo) of probable
dementia was 2.05 (95 percent CI 1.21-3.48). The absolute risk of developing
probable dementia with CE/MPA was 45 versus 22 cases per 10,000 women-years
compared with placebo.
Seventy-nine percent of the cases of probable dementia occurred in women that
were older than 70 for the CE alone group, and 82 percent of the cases of
probable dementia occurred in women who were older than 70 in the CE/MPA group.
The most common classification of probable dementia in both the treatment groups
and placebo groups was Alzheimer’s disease.
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
percent CI 1.19-2.60). Since both substudies were conducted in women 65 to 79
years of age, it is unknown whether these findings apply to younger
postmenopausal women. (See BOXED
WARNINGS and WARNINGS,
Dementia.)