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 March 1997

Specific Treatments:

oral contraception

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General Information

Estrostep, the first oral contraceptive (OC) in the a new class called Estrophasic has been approved. The Estrophasic OC phases in gradually increasing doses over the woman’s cycle. Estrophasic is the first new class of Ocs to be marketed in more than 10 years. Estrostep works by providing low, gradually increasing amounts of estrogen (20, 30, 35 mcg ethinyl estradiol) with a low, constant dose of progestin (one mg norethindrone acetate).

Monophasic birth control pills contain a constant doe of estrogen and progestin. Triphasics change the dose of progestin throughout the cycle while keeping the estrogen dose constant or increasing then decreasing the estrogen dose. This is the first OC that gradually phases in the estrogen component of the pill in increasing doses. With Estrostep, low doses of estrogen are phased into the woman’s body in three graduated steps during the menstrual cycle: 20 micrograms (mcg) of estrogen (ethinyl estradiol) 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.

When used as directed, Estrostep is greater than 99% effective in preventing pregnancy , as are all other combination Ocs.

Clinical Results

Estrostep was found to be well-tolerated in a clinical study involving 1,200 patients (769 receiving Estrostep), with a low overall drop-out rate due to side effects.

Side Effects

In addition to contraception, Estrostep, like all oral contraceptives, may also provide several health benefits including: lower incidence of ovarian cysts, lower incidence of pelvic inflammatory disease, reduced likelihood of developing cancer of the ovaries and cancer of the lining of the uterus, more regular periods, lighter menstrual flow and less menstrual discomfort.

However, all Ocs are also associated with certain side effects. Nausea/vomiting, breakthrough bleeding and headaches are common. Clinical studies with Estrostep showed that these side effects as well as weight gain each caused fewer than one percent of women to withdraw from therapy.

Additional Information

The most common pill prescribed today contains a constant 35 mcg estrogen dose. 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.

Oral contraceptives are not appropriate for all patients. The use of oral contraceptives is associated with some serious adverse side effects as well, such as increased risk of myocardial infarction, thromboembolism, stroke, hepatic neoplasia, and gallbladder disease. The risk of serious morbidity and mortality is very small in healthy women without underlying risk factors. It is important to note that oral contraceptives do not protect against HIV infection (AIDS) and other sexually transmitted diseases. Women who use oral contraceptives should be strongly advised not to smoke. Women should discuss the benefits and risks of Ocs with their healthcare provider.