The Food and Drug Administration has strengthened a warning about the risk of serious blood clots among women who use the Ortho Evra patch. The label for the birth control patch will now contain a warning about the risk of venous blood clots for Ortho Evra users. These clots may become life-threatening if they travel to the lungs, which may result in a pulmonary embolism.

Women who use the Ortho Evra patch are exposed to about 60% more estrogen than with birth control pills. According to the FDA, exposure to higher levels of estrogen can increase the risk of side effects, such as blood clots.

Although the Ortho Evra patch has contained warnings about the risk of blood clots with Ortho Evra since September 2006, the new warning is designed to clarify the information contained in that warning. The previous label contained information about two studies of the risk of Ortho Evra blood clots—one which found that patients were at twice the risk of blood clots compared with birth control pills, and another that found that the risks were similar with both.

However, after a recently completed third study also found that women who use Ortho Evra to be at an increased risk of blood clots or other side effects, the FDA ordered stronger warnings on the birth control patch.