WASHINGTON (CNN) -
The Food and Drug Administration on Thursday warned millions of women who use the Ortho Evra contraceptive patch that they are being exposed to about 60 percent more estrogen than with a typical birth control pill, which could put them at higher risk for blood clots.
The labels on the medication will be updated with the warning, the FDA said. Most daily birth control pills contain 35 micrograms of estrogen.
The patch releases ethinyl estradiol, an estrogen hormone, and norelgestromin, a progestin hormone, through the skin into the blood stream. The Ortho Evra patch only needs to be changed once a week and is the only patch approved for birth control.
The FDA said in a written statement that doctors and patients should weigh the increased exposure to estrogen against the chance of pregnancy if a birth control pill is not taken daily.
Ortho Evra is made by Johnson & Johnson (Research) subsidiary Ortho McNeil Pharmaceuticals.
In July, 10 women filed a lawsuit against the two companies, claiming the patch caused them to suffer strokes and blood clots. The lawsuit -- filed in Hudson County, N.J., Superior Court -- alleges that the patch is "defectively designed" and "unreasonably dangerous."
Women wearing the patch cite its ease of use. The thin, flexible, beige-colored patch can be placed on any of four areas of the body: the buttocks, abdomen, upper torso, excluding breasts, or upper arm.
About 4 million women have used the patch since its introduction in 2002.
Ortho McNeil is conducting additional studies to compare the risk of developing serious blood clots in women using Ortho Evra to the risk in women using typical birth control pills, the FDA said.
At the time the lawsuit was filed, Ortho McNeil said, "When used as labeled, Ortho Evra is a safe and effective birth control choice for many women.
"The safety of the patients who use our products is our first priority, and we take all adverse event reports seriously."
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