US regulators have opened the door to Wyeth’s new birth control pill Lybrel, marking the first oral contraceptive that also stops periods altogether to be approved.

Lybrel is made up of the hormones levonorgestrel and ethinyl estradiol, which are commonly used in other birth control products. But unlike many existing oral contraceptives on the market taken in 21-day cycles with a seven-day break, Wyeth’s drug is taken every day, which some believe will offer a more convenient option for women wishing to eliminate their periods.

Approval was based on a worldwide clinical trial programme involving 2,457 women, which showed that the drug had a comparable efficacy to rivals already on the market.

The safety profile was also similar to other oral contraceptives, with a higher risk of thromboembolic events such as blood clots and stroke. As part of a post-marketing commitment, Wyeth says it will carry out a study to assess women prescribed its product compared to those on cyclic oral contraceptives containing 20mcg ethinyl estradiol.

Long-term risks?

The company says that Lybrel has been geared towards “women who are seeking contraception and who are interested in putting their menstrual cycle on hold.” But, according to media reports, questions about halting the menstrual cycle as a matter of convenience are already being raised. To this end, regulators are also requesting that Wyeth investigates the long-term risks of suppressing menstruation, the US Food and Drug Administration’s Daniel Shames told Reuters.

Available by prescription, Lybrel is expected to be in US pharmacies in July 2007.