Washington For women, a new birth-control pill holds out the promise of ending the monthly curse. But it could take a year to work fully - and even then, the pill might not be right for all.
Called Lybrel, it's the first such pill to receive Food and Drug Administration approval for continuous use. When taken daily, the Wyeth pill can halt women's menstrual periods indefinitely and prevent pregnancies.
But the convenience can come with a trade-off and require persistence: Women probably will swap their regular period for irregular bleeding and spotting, though that decreases with time. Some may have to take the pill for a year before the bleeding vanishes.
The pill isn't for everyone, an FDA official said. About half the women enrolled in studies of Lybrel dropped out, said Dr. Daniel Shames, a deputy director in the FDA's drugs office. Many did so because of bleeding and spotting.
"If you think you don't want to go down this road, this is not for you," Shames told reporters.
Lybrel is the latest approved oral contraceptive to depart from the 21-days-on, seven-days-off regimen that had been standard since birth-control pill sales began in the 1960s. The pill is the first designed to put off periods altogether when taken without break.
Wyeth plans to start Lybrel sales in July. The Madison, N.J., company said it hasn't yet determined a price for the 28-pill packs. The pill contains a low dose of two hormones already widely used in birth-control pills, ethinyl estradiol and levonorgestrel.
A study showed Lybrel was just as effective in preventing pregnancy as a traditional pill, Alesse, also made by Wyeth. However, since Lybrel users will eliminate their regular periods, it may be difficult for them to recognize if they have become pregnant, Shames said.
Most of the roughly 12 million U.S. women who take birth-control pills do so to prevent pregnancy. Others rely on hormonal contraceptives to curb acne or regulate their monthly periods.
With Lybrel, in one test, 59 percent of the women who took Lybrel for a year had no bleeding or spotting during the last month of the study. However, because of dropouts, that translates into only about one-third of all the women originally enrolled in the study, Shames said.
"Women who use Lybrel would not have a scheduled menstrual period, but will most likely have unplanned, breakthrough, unscheduled bleeding or spotting," Shames said. The bleeding can last four to five days and may persist for a year, he added.