FDA warns about birth control pills

The US Food and Drug Administration (FDA) has ordered a safety review following links between birth control pills containing drospirenone and an increase in blood clots.

Brand names affected by the review include Beyaz, Safyral, Yasmin and Yaz [all Bayer]; Gianvi [Teva], Zarah [Watson] and Loryna [Sandoz].  The FDA has a full list of affected drugs.

The FDA said: "All birth control pills pose a risk of blood clots. Several epidemiological 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 the progestin levonorgestrel."

Drospirenone is a type of female sex hormone called a progestin, which works by preventing ovulation in a woman.

The FDA cited two recent studies that demonstrated a greater risk of blood clots for women taking birth control pills containing drospirenone compared to the risk in women taking birth control pills containing levonorgestrel - another progestin.

Previous studies that indicated no difference in the risk of blood clots between the two types of drugs were also noted by the agency.

The FDA said it is evaluating the conflicting results from the studies, and is analysing all currently available information to determine the risks and benefits of drospirenone-containing birth control pills.

The warning follows an announcement by the European Medicines Agency (EMA) in May 2011 that it is to update product information on oral contraceptives containing drospirenone and ethinyl estradiol regarding the risk of venous thromboembolism based on information from the same reports under analysis by the FDA.