The FDA approved yesterday the first continuous use birth control drug for women which, unlike other similar products, completely excludes the menstrual period.

The new contraceptive approved Tuesday by the Food and Drug Administration is called Lybrel and is manufactured by Wyeth of Philadelphia, PA. The product comes in a 28-day-pill pack and works the same way as the 21 days on, 7 days off cycle.

The significant difference from other birth control pills is that women taking Lybrel will not have a scheduled menstrual period. The drug will however cause unplanned breakthrough bleeding, or spotting, the agency warns.

Each pill of Lybrel contains a low-dose combination of 90 micrograms of a progestin, levonorgestrel, and 20 micrograms of an estrogen, ethinyl estradiol. These are active ingredients available in other approved oral contraceptives and, as with other birth control pills, continuous use stops the body's monthly preparation for pregnancy by lowering the production of hormones that make pregnancy possible.

The FDA approved Wyeth’s oral contraceptive based on two long-term clinical trials, each lasting one year. More than 2,400 women, ages 18 to 49, took Lybrel, proving its efficiency.

The downside is, on one hand, the spontaneous bleeding or spotting, which is very likely to happen, while on the other hand, due to the complete absence of a menstrual period, a woman taking Lybrel would not know if she is pregnant.

The federal agency advises women who suspect they may be pregnant to take a pregnancy test. The safety and efficacy study was published in the December 2006 issue of the journal Contraception.

The FDA said that in time the unscheduled bleeding decreases in women who have taken Lybrel for a full year. 59% of the participants in the first clinical study, who took Lybrel for a full year, experienced no bleeding/spotting during the last month of the study.

Wyeth says that according to studies undertaken, Lybrel did not delay a return to fertility. Return to normal menstruation was not affected either.

Side effects: increased risk of blood clots, heart attacks and strokes. The product carries a label warning: women who take the combination pill have an increased risk of serious cardiovascular problems if they also smoke cigarettes.

As with any other contraceptive product, women should discuss the use of Lybrel with their doctors. Lybrel is expected to be in US pharmacies in July 2007 and will be available by prescription only.