The Food and Drug Administration on Tuesday approved the first birth control pill designed to eliminate a woman's monthly period.
The new pill, called Lybrel, uses a combination of low-dose synthetic hormones used in other oral contraceptives now on the market. But all of the 28 pills that come in a monthly pack will contain active ingredients, forgoing the placebo tablets that normally allow menstruation to begin.
In the last four years, contraceptive makers have introduced a variety of products designed to minimize the frequency and duration of periods.
Yaz, made by Bayer HealthCare Pharmaceuticals, and Loestrin 24 Fe, from Warner Chilcott, came on the market last year with the promise of shortening periods to four days or less. Seasonale and Seasonique, sister products from Barr Pharmaceuticals, limit periods to four times a year.
Lybrel, from Wyeth Pharmaceuticals, takes the trend a step further by attempting to suppress periods altogether. The company plans to begin selling the pill in July.
"Why have a period at all?" said Dr. Gerardo Bustillo, assistant chief of obstetrics and gynecology at Orange Coast Memorial Medical Center in Fountain Valley.
But Lybrel doesn't quite reach that goal, based on the results of two clinical trials involving 2,400 women ages 18 to 49.
According to the FDA, the women experienced unscheduled breakthrough bleeding or spotting, though the incidence of such events decreased over time. In one study, 59% of women who took Lybrel for one year reported no bleeding during the last month. Many women stopped taking the pill after experiencing unscheduled bleeding.
In a European clinical trial, Lybrel prevented pregnancies in all 323 women who took it, according to Wyeth.
Birth control pills contain synthetic versions of estrogen and progestin that prevent ovulation. Without such production of an egg, a pregnancy cannot occur.
The national Centers for Disease Control and Prevention estimate that 11.6 million American women use birth control pills, but it is unclear how many might prefer a product like Lybrel.
"It's not for everybody," said Dr. Ricardo Azziz, chair of obstetrics and gynecology at Cedars-Sinai Medical Center in Los Angeles. "Some women like to have a period every month to reassure them that they are not pregnant. Some women may feel more 'natural' by having that period."
Azziz estimates that 20% to 30% of women on the pill take it in a way that minimizes their periods. That includes a substantial number who take conventional pills, which typically come in packs of 21 active tablets and 7 placebos, and skip the sugar pills at the end of the month.
Lybrel may appeal to women who take the pill to prevent such problems as menstrual cramps and migraine headaches, or to control endometriosis, Bustillo said.
"It's not like it's a disease to have a period, but for a lot of women it does cause problems," he said.
Wyeth and other drug companies say their research indicates many women want a pill to stop their periods. But product sales have not lived up to the drug makers' expectation.
Sales of Seasonale amounted to $100 million in 2006, or less than 1% of the $1.7-billion oral contraceptives market.
Analysts expect Lybrel sales to hit $40 million this year and grow to between $150 million and $250 million annually by 2010.
Wyeth has not said what it expects to charge for Lybrel, but birth control pills typically cost $20 to $45 a month.
Times staff writer Daniel Costello contributed to this report.