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conjugated estrogens (Premarin): Drug Facts, Side Effects & Dosage

What is Premarin? What is Premarin used for?

Estrogens are one of the two major classes of female hormones. (Progestins comprise the second major class). Estrogens are used primarily to treat the symptoms of menopause and states in which there is a deficiency of estrogen, for example, among women who have had their estrogen-producing ovaries removed. Conjugated estrogens are a mixture of several different estrogens (estrogen salts) that are derived from natural sources and blended to approximate the composition of estrogens in the urine of pregnant horses. The main components are sodium estrone sulphate and sodium equilin sulfate. Estrogens have widespread effects on tissues in the body. Estrogens cause growth and development of the female sexual organs and maintain female sexual characteristics such as the growth of underarm and pubic hair, body contours, and skeleton. Estrogens also increase secretions from the cervix and growth of the inner lining of the uterus (endometrium). Conjugated estrogens were first approved by the FDA in 1938.

What brand names are available for conjugated estrogens vaginal cream?

Premarin Vaginal Cream

Is Premarin cream available as a generic drug?

No

Do I need a prescription for Premarin?

Yes

What are the side effects of Premarin?

Among the most common endocrine side effects are:

  • breakthrough vaginal bleeding
  • spotting,
  • loss of periods,
  • excessively prolonged periods,
  • breast pain or
  • breast enlargement, and
  • changes in sexuality (increases or decreases in libido).

Other important side effects include:

Melasma–tan or brown
patches– may develop on the forehead, cheeks, or temples. These may persist
even after the estrogen is stopped.

Conjugated estrogens may increase the
curvature of the cornea, and patients with contact lenses may develop
intolerance to their lenses.

Blood clots are an occasional, serious side effect
of estrogen therapy and are dose-related. (The higher the dose of estrogen, the
greater the risk of blood clots.) Cigarette smokers are at a higher risk than
non-smokers for blood clots, and patients requiring estrogens should be
encouraged to
quit smoking.

Estrogens can promote thickening of the lining of
the uterus (endometrial hyperplasia) and increase the risk of uterine cancer. At
diagnosis, endometrial cancers in recipients of estrogens are generally at an
earlier stage and are less aggressive when they are discovered. Survival from
endometrial cancer also is better in women taking estrogens than in those not
taking estrogens. The addition of a progestin to estrogen therapy offsets the
risk of endometrial cancer. Conflicting data exists on the association between
estrogens and breast cancer. There may be a small increase in risk. The effect
of concomitant progestin therapy on the risk of estrogen-induced breast cancer
is unclear. Conjugated estrogens are well-absorbed from the vagina and into the
blood. The amount absorbed depends on the frequency of use and the amount used.
Thus, more frequent use or larger amounts of vaginal estrogens can have effects
throughout the body (see conjugated estrogens, Premarin). The Women's Health
Initiative found that postmenopausal women (50-79 years old) taking conjugated
estrogens had an increased risk of breast cancer, blood clots, and stroke. There
was also an increased risk of impaired cognition and/or dementia among women
over age 65.

What is the dosage for Premarin cream?

The recommended dose is 0.5 to 2 grams administered daily for
21 days then off for 7 days. Twice weekly administration may also be used.
Vaginal products work best if used at bedtime. The hands should first be washed
and the applicator filled with cream from the tube. Lying on the back with the
knees bent, individuals should insert the applicator into the vagina and push
the applicator's plunger to deliver the cream. The applicator and plunger then
should be washed with warm, soapy water and rinsed with plain water. The hands
should be washed before and after use. A small amount of the cream also can be
applied to the outer skin folds or "lips" of the vagina (vulvae) to relieve
dryness or irritation.

Which drugs or supplements interact with Premarin cream?

Premarin drug interaction studies have not been
conducted. Estrogens are broken down in the liver by certain enzymes. Drugs that
increase or decrease the activity of these enzymes may interfere with the action
of Premarin. Rifampin (Rifadin), barbiturates, carbamazepine (Tegretol),
griseofulvin (Grifulvin), phenytoin (Dilantin), St. John's wort, and primidone
may increase the elimination of estrogen by enhancing the liver's ability to
eliminate estrogens. Use of any of these medications with estrogens may result
in a reduction of the beneficial effects of estrogens. Conversely, drugs such as
erythromycin, ketoconazole (Nizoral), itraconazole (Sporanox), and ritonavir (Norvir)
may reduce the elimination of estrogens by the liver and lead to increased
levels of estrogens in the blood and increased effects. Grapefruit juice also
may increase levels of estrogen by increasing the absorption of estrogens from
the intestine. Increased levels of estrogens in the blood may result in more
estrogen-related side effects.

Is Premarin cream safe to take if I’m pregnant or breastfeeding?

Estrogens should be avoided
during pregnancy since they
increase the risk of fetal abnormalities.

Estrogens are secreted in milk and cause
unpredictable effects in the infant. In general, they should not be used by
women who are breastfeeding.

What else should I know about Premarin cream?

What preparations of Premarin cream are available?

0.625 mg/gram

How should I keep Premarin stored?

The cream should be stored at room temperature, 15-30 C
(59-86 F).

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