Safety concerns with the popular birth control pill Yaz increased Thursday as federal health scientists reported that the Bayer drug and other newer birth control treatments appear to increase the risk of dangerous blood clots more than older medications.
A new study released by the Food and Drug Administration reviewed the medical history of more than 800,000 U.S. women taking different forms of birth control between 2001 and 2007. On average, woman taking Yaz had a 75 percent greater chance of experiencing a blood clot than women taking older birth control drugs.
Yaz contains estrogen along with a next-generation synthetic hormone called drospirenone, which is known to increase potassium levels in the blood. FDA compared medical records of women taking the drug with those taking the older drug levonorgestrel.
Yaz, Yasmin and related drospirenone-containing pills were Bayer's second-best-selling franchise last year at $1.6 billion in global sales.
In 2009, the FDA took the unusual step of ordering Bayer to run corrective TV advertisements on Yaz, saying the drugmaker's marketing campaign overstated the drugs' ability to prevent acne and premenstrual syndrome.
The agency also reported higher complications in women using the Ortho Evra patch from Johnson & Johnson and the Nuvaring vaginal ring from Merck & Co. Inc. Those drugs combine estrogen, which is present in all birth control pills, with two other synthetic hormones launched in the last decade.
The FDA said it hasn't reached a final conclusion on the drugs' safety but will hold a meeting with scientific advisers Dec. 8.
Recent studies have reached differing conclusions on the risks of newer birth control pills.
A study published earlier this week involving more than 1 million Danish women found that women taking Yaz and other newer medications had twice the risk of blood clots as women taking the older hormone levonorgestrel.
However, two studies published in 2007 did not find any difference in blood clotting between the two comparable groups.