The U.S. Food and Drug Administration (FDA) has announced that it is looking at results from two studies that showed there is a higher risk of blood clots in women taking new birth control pills containing the compound drospirenone. Some brand names include Yaz, Yasmin, Beyaz, Ocella, Loryna, Gianvi, Safyral, Syeda and Zarah.
Bayer AG's best-selling birth control drugs, including Yaz and Yasmin, contain the compound. The two studies in question studies looked at whether there is a higher risk of blood clots in women taking birth control pills containing drospirenone, when compared to similar women taking pills containing a different compound called levonorgestrel. The studies showed the risk of blood clots is reported to be up to 2 to 3 times greater than levonorgestrel-containing pills. The most recent studies were published earlier this year in the British Medical Journal.
Most birth-control pills contain two types of hormones, estrogen and progestin. All types of pills increase the risk of blood clots. The FDA said some previous studies have reported that the risk of blood clots for women who use birth-control pills containing drospirenone is higher than that for women who use birth-control pills containing levonorgestrel, while other studies haven't found such a risk. While the risk of blood clots is low among women who take birth-control pills, the FDA said it is higher than the risk among women who aren't taking the pills.
In the women taking the pills the blood clots form inside a vein and are known as deep vein thrombosis, or DVT. The clots usually form in the lower leg or thigh, but can break loose and travel to other areas of the body such as the lungs, where they are called a pulmonary embolism, or PE. The FDA said the symptoms of a DVT include the new onset of persistent leg pain, while those of a PE include severe chest pain and sudden shortness of breath.
The FDA said it is “currently evaluating the conflicting results from these studies and will look at all currently available information to fully assess the risks and benefits of drospirenone-containing birth-control pills.” An FDA-commissioned study exploring the association of blood clots with hormonal contraception is in the process of being finalized and reviewed. The study involves more than 800,000 U.S. women and results are expected later this summer.
The manufacturers meanwhile defended saying its analysis of the available scientific evidence shows that the risk of developing a blood clot associated with taking pills containing drospirenone “is comparable” to that of other birth-control pills studied. The company said it “will continue to work closely with the FDA on this matter.” Sales of Bayer's Yaz product family have been declining, which the company blames on generic competition in the U.S. Yaz-related sales fell nearly 16% to €242 million ($348 million) in the first quarter after dropping 13% in 2010.
The EMA or the European Medicines Agency also announced last week that the risk of developing blood clots for oral contraceptives containing drospirenone was higher than that of pills containing levonorgestrel but said the risk for any type of birth-control pill was small. EMA said the product labels of birth-control pills containing drospirenone will be updated.