Warnings about blood clots with contraceptive patch

According to U.S. regulators, Johnson & Johnson's Ortho Evra contraceptive patch contains higher levels of a hormone known to cause blood clots than average birth control pills.

The U.S. Food and Drug Administration says new labeling for the patch will include information about the higher levels of estrogen, but that it is unclear whether women using the once-a-week product are more at risk for clots.

The FDA believes that women who use the Ortho Evra patch are exposed to 60 percent more estrogen than those who use the pill.

But the pills, which contain several variations with different hormone levels for use during one month, can contain a higher maximum amount of estrogen.

The FDA says that women taking or considering using the product should work with their health care providers to balance the potential risks related to increased estrogen exposure against the risk of pregnancy if they do not follow the daily regimen associated with typical birth control pills.

As yet there has been no comment from J&J's Ortho McNeil Pharmaceuticals unit, which makes the patch.

The FDA does say that Ortho McNeil is currently conducting studies comparing the blood clot risk in women using its patch compared to those taking typical birth control pills containing 35 micrograms of estrogen.

The agency says it will also continue to monitor for safety problems.

Ortho Evra, the first contraceptive patch on the U.S. market, releases the estrogen hormone ethinyl estradiol and a progestin hormone norelgestromin into the blood stream through the skin.