Risks of blood clots in legs and lungs are twice as high for women using the birth-control patch instead of the pill, says a study reported by the drug maker and the Food and Drug Administration.
Dr. Daniel Shames of the FDA said Friday the new findings don't require immediate action by the government, but he urged concerned women to discuss the risk with their physicians.
One new study found users of the Ortho Evra patch had twice the risk of clots compared with women taking birth-control pills, although a second analysis found no difference in risk between the two forms of birth control.
"For some people, the patch may be better because some people don't reliably take the pill, or don't want to take the pill or forget the pill," Shames said. "So the patch does offer them some alternative for contraception."
"On the other hand, we need to interpret what these results mean," he said. "But these results are preliminary, so we can't make hard comments about it."
This isn't the first time problems have the patch have been reported. Dozens of lawsuits have been filed on behalf of women who claim serious side effects, and CBS News reported last November documents released by Ortho McNeil as part of one of those suits appear to indicate a much higher risk that even the numbers revealed today.
Over a two-year period, more than 500 serious side effects were reported by women using the patch, including blood clots, strokes and heart attacks, reports CBS News correspondent Cynthia Bowers.
The results of the two studies were made public Thursday by the patch's manufacturer, Ortho Women's Health & Urology. The Raritan, N.J.-based company is owned by Johnson & Johnson.
Last year an investigation by The Associated Press, citing federal death and injury reports, found higher rates of blood clots in women using the patch.
While one of the newly reported studies found no increased risk of clots, the interim results from the second suggested a twofold increase in the risk of venous thromboembolic events, or clots in the legs and lungs, in women using the patch, Ortho said.
However, because the confidence intervals of the results for the two forms of contraceptive overlap, there actually may be no increased risk from the patch or it may be more than double, said Shames, FDA's director for reproductive and urologic drug products.
He said the risk of a nonfatal blood clot is about one per year in 10,000 women not using a contraceptive. For those using a hormonal contraceptive such as the patch or pill, the risk rises to between three and five per 10,000, he said.
"These are fairly unusual events," said Shames. He noted that in pre-approval testing of the patch on about 3,000 women there were two reports of blood clots, but one involved a woman who had had surgery.
The ongoing studies also are looking at the risk of heart attacks and strokes among users of the two types of contraception. Currently there is no difference but the numbers are small and it will take another 18 months to see if a difference occurs, Shames said.
The company said the risk of clots remains rare and that they have been reported as a potential risk of all hormonal contraceptives.
Release of the interim results comes four months after the FDA warned women that the increased levels of hormones released by the patch put them at higher risk of blood clots and other serious side effects.
Additions to the patch label made in November warned women that they would be exposed to about 60 percent more estrogen than those who use birth-control pills.
Since the patch went on sale in 2002, more than 4 million women have used it.
The investigation by The Associated Press found that patch users die and suffer blood clots at a rate three times higher than women taking the pill. About a dozen women died in 2004 from blood clots believed linked to use of the patch, the AP reported. Dozens more suffered strokes and other clot-linked problems.
Health officials warn that women who smoke should not use the patch, since smoking increases the risk of stroke and heart attack.