Early Studies Tie Birth Control Patch to Blood ClotsFeb 17, 2006 | Los Angeles Times
Women using the increasingly popular birth control patch may face double the risk of blood clots than women taking the pill, but more investigation is needed to see if the preliminary findings are valid, federal regulators said today.
"We're not sure what this means clinically, but it's information that people need to know about," said Dr. Daniel Shames, who heads the Food and Drug Administration division that evaluates contraceptives.
Blood clots usually form in the legs, and sometimes, the lungs. They can travel to the heart or the brain, causing heart attacks and strokes. But the overall risk of blood clots among women taking birth control pills is low, about three to five cases for every 10,000 women treated for a year.
"At this time, we do not plan on taking any specific regulatory action based on these preliminary results," Shames added.
Manufacturer Ortho-McNeil Pharmaceutical, Inc. said it is cooperating with the FDA in the ongoing scientific investigation. The company, a division of Johnson & Johnson, sponsored the research that is raising concern. Sales of the patch totaled more than $400 million in 2004, according to DrugTopics.com, an industry website.
Marketed as Ortho Evra, the birth control patch has been used by more than 4 million women since the FDA approved it in late 2001. It works by releasing estrogen directly into the bloodstream through vessels near the surface of the skin. While contraceptive pills have to be taken daily, a woman can wear one patch for seven days.
Since estrogen can promote the formation of blood clots, women taking any hormonal contraceptive run the risk of such side effects. But with the patch, the total level of estrogen exposure is 60% higher than with a typical birth control pill, according to the FDA.
"Because it is absorbed directly through the blood as opposed to a pill taken by mouth...the total exposure is more," said Shames.
The FDA issued a warning last November about the higher levels of estrogen with the patch. The latest worries come after two separate safety studies commissioned by the manufacturer produced seemingly contradictory results.
A recently published study by the Boston Collaborative Drug Surveillance Program found no higher risk of blood clots among women using the patch than among those taking the standard dose of birth control pills.
But preliminary findings from a second study, by i3 Drug Safety, found a two-fold increase in the risk of blood clots in the legs and lungs for women using the patch. Complete data from the second study has not been publicly released.
Both studies used insurance claims data to track the experiences of tens of thousands of women using the medications. Researchers also were looking into whether women using the patch face a higher risk of heart attacks and strokes, although preliminary data suggest that they do not, the company said. FDA officials said long-term studies may be needed to pinpoint the risk.
Last year, an Associated Press analysis of FDA reports of serious drug side effects indicated that women using the patch faced a three times higher risk of dying or suffering a blood cut than those taking birth control pills.
Some critics of the agency say the potential for harm should have been clear in clinical trials before the patch was approved.
"It is no more effective than the pill and has a higher risk because it delivers significantly more estrogen," said Dr. Sidney Wolfe of the Public Citizen advocacy group.
The FDA's Shames said the drug was tested on 2000-3,000 women before it was approved, and two suffered serious blood clots. One patient had undergone surgery, he said, so it was unclear if her problems could be blamed on the patch. "Statistically, it had no meaning," said Shames.
But the Associated Press reported that at the time that the cases had alarmed an FDA drug reviewer, who recommended that patients and doctors be clearly advised of the risk, and follow-up safety studies be conducted.
Susan Wood, a former head of the FDA women's health office, said the agency "still doesn't have enough data to make a call" on the safety of the patch.
Wood said women using the patch should weigh the new information on risks against their individual circumstances, including their health and how they use birth control. Wood resigned from the agency last year to protest delays in approving the "morning after" contraceptive for sale without a prescription.
"Women should be aware that (the patch) does have a higher estrogen level and this potentially can lead to greater side effects," she said. "But the increase in risk, even if real, would still be fairly low. This is more information that is helpful, but it is not something that should send women off their birth control method."