FDA ( Food and Drug Administration ) has reviewed six published epidemiologic studies that evaluated the risk of venous thromboembolism ( VTE ) in women using birth control pills containing Drospirenone. These studies have conflicting findings. Two were postmarketing studies required by the FDA or European regulatory agencies. These studies did not report any difference in venous thromboembolism risk between Drospirenone-containing products and products containing Levonorgestrel or other progestins.
Two publications from 2009, however, reported a 1.5- to 2-fold higher VTE risk in women who use Drospirenone-containing contraceptives as compared to the risk in women who use Levonorgestrel-containing contraceptives.
More recently, two articles published in 2011 in the British Medical Journal reported a 2- to 3-fold greater risk of blood clots in women using oral contraceptives containing Drospirenone rather than Levonorgestrel. As with all epidemiologic studies, there are methodological issues that make interpretation of these conflicting results complex.

FDA has not reached a conclusion on the risk for blood clots in women using drospirenone-containing birth control pills, but remains concerned about the potential increased risk.

Initial data from an FDA-funded epidemiologic study exploring the association of blood clots with several different hormonal contraceptive products, including Levonorgestrel-containing contraceptives, appear consistent with results from the 2009 and 2011 published studies.
Although FDA's review is ongoing, the preliminary data from the FDA-funded study are consistent with an approximately 1.5-fold increase in the risk of blood clots for users of Drospirenone-containing contraceptives compared to users of other hormonal contraceptives. To put this risk into perspective, if the risk of developing a blood clot among women using other hormonal contraceptives is about 6 women in 10 thousand, then the risk of developing a blood clot among women using Drospirenone-containing oral contraceptives would be about 10 women in 10 thousand.

The available studies have only examined the risk of venous thromboembolism in users of contraceptive pills that contain Drospirenone and 0.03 mg of Ethinyl Estradiol and not other pills that contain Drospirenone combined with a lower dose of Estrogen ( e.g., 0.02 mg Ethinyl Estradiol ). It is unknown at this time whether the reported venous thromboembolism risk applies to all Drospirenone-containing products.

Source: FDA, 2011

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