It was already known that the Ortho Evra® birth control patch causes blood clots.

Now, the maker of the patch is saying that overweight women using the birth control patch Ortho Evra® are at a particularly high risk of developing blood clots.

Janssen-Ortho Inc. (part of Johnson & Johnson; NYSE: JNJ), also warns that women should not expose the Ortho Evra® birth control patch to sources of heat such as saunas and whirlpools, based on what the company calls a theoretical risk that doing so might cause an unintentional increase in estrogen exposure.

Currently, no such precautions exist for a similar birth control patch sold to women in the United States but these new warnings were endorsed by Health Canada, the Canadian agency responsible for ensuring the safety and effectiveness of pharmaceutical products in that country.

In September 2006, Johnson & Johnson updated the label information for Ortho Evra to warn users of blood clots, stroke and other medical complications. The updated warning was based in part on a study that showed women using the patch were twice as likely to experience blood clots as were those who took a traditional contraceptive pill.

Canadian manufacturer Janssen-Ortho Inc. markets Ortho Evra® in the United States: a patch designed to prevent pregnancy by delivering the hormones estrogen and progestin through the skin.

Think twice about using the patch, i still don't know what happened to the lawsuit filed by Ortho Evra® patch users.

Find more details from the press release.