Wyeth said that the contraceptive is suitable for women who are interested in putting their menstrual cycle on hold, as the drug provides a steady low dose of hormones so that over time women may become cycle-free.
The company said that worldwide clinical trials involving 2,457 women demonstrated the efficacy of Lybrel, which showed comparable contraceptive efficacy similar to other FDA-approved oral contraceptives.
Wyeth revealed that while 59% of women taking Lybrel during the trial experienced no bleeding or spotting, 21% of women required sanitary protection due to breakthrough bleeding. A number of women left the trials due to this side-effect.
The company warned that unscheduled bleeding or spotting is likely to occur while Lybrel is taken, especially during the first three to six months, and added that as there is no monthly cycle, unwanted pregnancies would be harder to distinguish.
Wyeth expects Lybrel to be in US pharmacies in July 2007 and said that as part of its post-marketing commitment, the company will conduct a study of thromboembolic events among women prescribed Lybrel, compared to women prescribed cyclic oral contraceptives containing 20mcg of ethinyl estradiol.