FRIDAY, Feb. 17, 2006 (HealthDay News) -- Preliminary study results suggest that women who use the Ortho Evra birth-control patch may face twice the risk of developing blood clots as women who take a contraceptive pill.
Another study, however, showed that the risk was roughly the same between the two groups.
Although the U.S. Food and Drug Administration discussed the results of the studies Friday, agency officials said they aren't planning any immediate action other than to suggest that women consult their doctors.
"At this time, we do not plan on taking any specific regulatory action based on preliminary results," Dr. Daniel Shames, director of the division of reproductive and urologic drug products at the FDA's Center for Drug Evaluation and Research, said during a Friday news conference.
"Further evaluation is necessary to see what the results mean. We don't know the answer yet," he added. "After the company looks at the data more rigorously, we may have different information and we may make different recommendations."
After receiving reports of adverse events related to Ortho Evra, the FDA asked the maker, Ortho Women's Health and Urology, owned by Johnson & Johnson, for more controlled epidemiological studies. The company commissioned two groups to perform the two new studies.
The first study, conducted by the Boston Collaborative Drug Surveillance Program at Boston University School of Medicine and involving about 200,000 women, found that the incidence of non-fatal blood clots was about the same between Ortho Evra and a birth control pill. The findings on risk of stroke and heart attack are not available yet.
But the second study, conducted by a different group of researchers and using a different group of women, found a two-fold risk increase in the Ortho Evra group.
"It may be that the incidence rates between the two groups are essentially the same or it may be double in one group," Shames said.
Women using contraceptives face a risk of non-fatal clots of about three to five per 10,000 women years, compared to one per 10,000 women years for those not taking a contraceptive, Shames said. A "woman year" refers to a woman on a contraceptive for one year.
Four months ago, the FDA changed the label on the patch to reflect that women using it had a higher risk of blood clots and other side effects because they are exposed to more estrogen than women taking the pill.
According to the Associated Press, more than 4 million women have used the patch since it went on the market in 2002.
Final analysis of the new data may be available by May, Shames said. It will then take 18 months to determine if there is a difference between groups in the incidence of heart attacks and strokes, he said.
Women who smoke should not use the patch because smoking increases the risk of stroke and heart attack.
FDA officials recommended that women discuss the issue with their health-care provider.
"For some people, the patch may be better," Shames said. "On the other hand, we need to interpret what these results mean. They are just preliminary so we can't make very hard comments."
Visit the FDA for more on the birth control patch.