According to a recent study, women who use the Ortho Evra birth-control patch are at double risk of developing blood clots than those taking oral contraceptives, the Food and Drug Administration said Friday.
However, the agency said that presented results are preliminary and hence they do not require prompt action other than advising women to discuss the risk with their physician.
The results of the research, along with another that reealed no greater risk, were made public on Thursday by the patch’s producer.
"The results are preliminary and further evaluation is necessary to understand what these results mean," said Dr. Daniel Shames, director of the division of reproductive and urological drug products at FDA.
The results come from one of two analyses comparing the patch and pill, said Ortho Women’s Health & Urology, manufacturer of the once-a-week patch. The Raritan, N.J.based company is owned by Johnson & Johnson.
An investigation conducted last year by The Associated Press, citing federal death and injury reports, found higher rates of blood clots in women using the patch.
Ortho said that the first research discovered no greater risk of clots but the interim results from the second study indicated a double rise in the risk of venous thromboembolic events, or clots in the legs and lungs, in women using the patch.
However, because the confidence intervals of the results for both forms of contraceptive overlap, there may be no increased risk from the patch or it may be more than twice, Shames said at a briefing.
He said the risk of a nonfatal blood clot is about one annually in 10,000 women not using birth control medications. For those using a hormonal contraceptive such as the patch or pill the risk increases to between 3 and 5, he added.
"These are fairly unusual events," said Shames. He pointed out that in preapproval testing of the patch on about 3,000 women there were 2 reports of blood clots, but only one involved a woman who had undergone surgery.
The current research also is looking at the risk of heart attacks and strokes among users of both types of contraception. According to Shames, at present, there is no difference but the numbers are small and it will take another 18 months to see if any difference appears.
The company claimed that the risk of clots remains very rare and that they have been reported as a potential risk of all hormonal contraceptives.
The interim results appear 4 months after the Food and Drug Administration warned women that the higher levels of hormones released by the patch increase their risk of blood clots and other serious side effects. Ortho said it shared the results of the latest research with the FDA.
The patch label issued in November warned women that they would be exposed to about 60% more estrogen than those using birth control pills.
Since 2002 when the patch went on sale, more than 4 million women have used it.
The study conducted by The Associated Press discovered that patch users die and suffer blood clots at a 3 times higher rate than women taking the pill. About 12 women died in 2004 from blood clots associated with the use of the patch, the AP reported. Dozens more suffered strokes and other clot-linked conditions.
Health officials warn that women who smoke should not use the patch, as smoking enhances the risk of stroke and heart attack.
