June 2, 2011 -- The FDA has issued a safety alert warning that women taking a newer type of birth control pill containing the progestin hormone drospirenone may be at higher risk for developing potentially deadly blood clots than women taking pills with an older type of progestin hormone.
The FDA says in a statement that its decision to investigate the birth control pills was based on two newly published studies. Those studies suggested that an increased risk for blood clots may exist in women taking pills containing drospirenone, a synthetic version of the hormone progestin, as compared to women taking birth control pills that contain levonorgestrel, another version of progestin.
Based on data from the two new studies, the FDA says, “This risk is reported to be up to two to three times greater than the risk of [venous thromboembolism] associated with using levonorgestrel-containing pills.”
FDA Suggests Women Taking Pills Contact Their Doctors
The FDA also says, however, that other studies have not reported an increased risk, and that women taking the pills with drospirenone should not stop taking them without first consulting their doctors.
Blood clots are a well known possible side effect of all birth control pills, though the risk is small.
The FDA says it is reviewing results of a large study involving more than 800,000 women that it commissioned to study risks associated with general oral contraceptive use. The agency says it will continue to keep the public informed as analysis of the new study becomes available.
The agency explains that drospirenone is a type of female sex hormone called a progestin. Most birth control pills contain two types of hormones, estrogen and progestin. The pills work in part by preventing the release of eggs from the ovaries and changing the lining of the uterus.
The FDA says that women who smoke and who are over age 35 “should not take combination oral contraceptives because they increase the risk that you could experience serious cardiovascular events, including blood clots.”