The U.S. Food and Drug Administration (FDA) issued a safety announcement  informing the public that the agency is  evaluating birth control pills that contain drospirenone. The review will  evaluate the risk of blood clots in women who use these products.

Drospirenone, a type of female sex hormone called a progestin, is found in most birth control pills with estrogen. All birth control pills pose a risk of blood clots but several epidemiological studies report 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 the progestin, levonorgestrel. Other studies have not reported an increase in risk.

A blood clot that forms in a deep vein in the body is called a deep vein thrombosis (DVT), a rare side effect of taking birth control pills. A blood clot can break loose from the vein, move through the body to the lung, and cause a pulmonary embolism (PE), which can lead to death.

Other  studies had conflicting findings--two post-marketing studies required by the FDA or European regulatory agencies did not report any difference in the risk of blood clots between drospirenone-containing products and products containing levonorgestrel or other progestins.

Two other publications in 2009, however, reported that the risk of blood clots is higher in women using drospirenone-containing products than in women who use levonorgestrel-containing products. Information from these studies is contained in the Warnings and Precautions section of labels of current products

An additional large study exploring the association of blood clots with hormonal contraception has been commissioned by FDA, and results of that study are being finalized and reviewed.

The European Medicines Agency (EMA) announced  it is updating the product information on oral contraceptives containing drospirenone and ethinyl estradiol regarding the risk of venous thromboembolism after review of all available data, including the data the FDA is reviewing.

The FDA is evaluating the conflicting results from these studies and will look at all available information to fully assess the risks and benefits of drospirenone-containing birth control pills.

 Release Date: May 31, 2011
Source: The United States Food and Drug Administration