Estrostep (norethindrone acetate and ethinyl estradiol)

The following drug information is obtained from various newswires, published medical journal articles, and medical conference presentations.


Approval Status:

Approved October 1996

Specific Treatments:

oral contraceptive

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General Information

Estrostep, a graduated Estrophasic oral contraceptive, has been approved as an oral contraceptive. Other birth control pills usually contain a constant dose of estrogen and progestin, or change the dose of progestin throughout the cycle. Estrostep is the only oral contraceptive to combine low, gradually increasing amounts of estrogen (20, 30, 35 mcg ethinyl estradiol) with a low, constant dose of progestin (one mg norethindrone acetate). When used as directed, Estrostep is greater that 99% effective in preventing pregnancy, as are all other combination OC's.

Early generation pills contained doses of estrogen as high as 150 mcg. Studies linking high doses of the hormone to adverse effects have resulted in a progressive reduction of estrogen content, leading to today's low-dose pills. The most common pill prescribed today contains a constant 35-mcg-estrogen dose.

With Estrostep, graduated amounts of estrogen are introduced into the woman's body in three phased-in doses during each menstrual cycle: 20 mcg of estrogen for the first five days, 30 mcg for the next seven days, and 35 mcg for the last nine days, for a total of 21 days. Estrogen and progestin are stopped for the remaining seven days of the cycle, resulting in a woman's monthly menstrual period. The 28-day pill pack will contain seven inactive tablets to help women maintain their regimen.

Clinical Results

While both estrogen and progestin play a role in the efficacy of combination OC's, the estrogen component also contributes to maintaining menstrual cycle control. Clinical studies of Estrostep show that its unique graduated low estrogen doses are sufficient to provide good endometrial support. Few women in these studies discontinued Estrostep due to missed periods and breakthrough bleeding. These particular complaints are frequent among women who are trying the pill for the first time.

In a comparative clinical study involving more than 1,200 women (769 receiving Estrostep), Estrostep was shown to have a high degree of patient acceptance, with a side effect profile comparable to other low-dose OC's.

Side Effects

OC's are associated with side effects. Nausea, vomiting, and breakthrough bleeding are common side effects that may subside within the first three months of use. Clinical studies with Estrostep showed that weight gain and nausea each caused less than one percent of women to withdraw from therapy.