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Period-blocking Pill Shows Promise

New drugs offer option to women who can't take estrogen

FRIDAY, July 27, 2001 (HealthDayNews) -- Women who'd rather avoid their periods may soon be able to take new drugs that block menstruation, prevent ovulation and stop harmful buildup of uterine cells.

Scientists in the United States and Germany say compounds that interfere with the hormone progesterone can shut down periods and halt ovulation in monkeys, yet the effects are reversed easily in two to six weeks.

The researchers say the drugs, called antiprogestins, are not on the market yet, but probably will work in women.

Monthly periods can be more than a nuisance. They can produce severe mood swings, abdominal pain, excessive bleeding and a range of other symptoms many women wouldn't miss.

Low-dose oral contraceptives, which combine the reproductive hormones estrogen and progesterone, often are used to put off ovulation. Yet some women don't respond well to the pills, which can also up the risk of blood clots and other potentially serious side effects.

In the latest study, Robert Brenner of Oregon Health and Science University's Primate Research Center looked at varying doses of two antiprogestins -- ZK 137 316 and its more potent sibling, ZK 230 211.

The drugs prevent the reproductive hormone progesterone from linking up with its molecular receptors. Progesterone helps trigger ovulation, and prepares the uterus for implantation of a fertilized egg. The abortion pill Mifeprex, or RU-486, is an antiprogestin compound.

Brenner's group chose rhesus macaque monkeys for the study because their menstrual cycles closely mimic those of women.

Monkeys that received ZK 137 316 ovulated but failed to menstruate, while those on the second compound did neither, Brenner's group says. Both drugs also kept estrogen from dangerously thickening the lining of the uterus, a condition called endometriosis that can cause pain, bleeding and even infertility.

Brenner says the drugs could provide an alternative to women who want to suppress their periods but can't take estrogen. They also might help women who resort to surgical removal of their wombs because of excessive menstrual bleeding.

"I see this approach as being a way to save a woman's uterus, save her from going through surgery by suppressing this excessive bleeding. That's the kind of study in women that ought to be done," he says.

Dr. Leslie Miller, a University of Washington gynecologist, says drugs that block progesterone are a promising option for women who'd like to avoid monthly bleeding. However, Miller, who has recently studied bleeding patterns in women, says taking continuous doses of birth control pills can accomplish the same thing as the new drugs; however, she says regulators haven't approved oral contraceptives for continuous use.

On the other hand, Miller says some women who aren't good candidates for estrogen might want to take an antiprogestin pill, including smokers over 35, women with a history of heart attacks, strokes or blood clots and those who are breast-feeding.

"That would be a big reason why someone would want a progesterone receptor antagonist," she says.

Miller says women who want to get pregnant wouldn't want to stop having periods, but for the 15 million American women on birth control pills, the pause in pill-taking that leads to bleeding is essentially symbolic.

"Women taking birth control pills are not having real periods. They're getting a sign each month that they're not pregnant," she says.

What To Do: For more about whether you should stop having periods, go to No Period. For more on menstruation, check the Museum of Menstruation and Women's Health.

SOURCES: Interviews with Robert Brenner, Ph.D., senior scientist, Oregon Regional Primate Research Center, Oregon Health and Science University, Beaverton, Ore.; Leslie Miller, M.D., assistant professor, women's health, University of Washington School of Medicine, Seattle; Aug. 1, 2001, Human Reproduction
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