Ortho-McNeil is currently facing more than 500 birth control patch lawsuits from former users of the Ortho Evra patch. But experts say that this number may rise sharply in the coming months because of a Food and Drug Administration study which examines the side effects of Ortho Evra.

The FDA study says that women using the Ortho Evra patch face twice the risk of blood clots compared with users of birth control pills. This in turn raises a woman’s risk of other birth control patch side effects, including stroke and heart attack. The FDA study confirms the results of an Associated Press investigation in 2005, which also found that women who use Ortho Evra face an increased risk of birth control patch side effects like blood clots.

The increased risk of Ortho Evra side effects comes because 60% higher estrogen dose that women using the patch receive compared to birth control pills. Because estrogen increases blood clotting, women using the Ortho Evra patch are at an increased risk for other birth control patch side effects linked with blood clots.

There have been more than 100 injuries and more than a dozen birth control patch deaths among users of the Ortho Evra patch. Media coverage of these Ortho Evra side effects and FDA updates to the patch’s warning label have caused sales of Ortho Evra to decline significantly. But despite evidence of the increased health risks associated with patch, neither the FDA or Ortho-McNeil has issued an Ortho Evra recall.