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Blood Clot Risk Increased in Women Taking Birth Control Pills Containing Drospirenone
An FDA-funded study led by the Kaiser Permanente Northern California Division of Research has found an increased risk of venous thromboembolic events (VTEs) and arterial thrombotic events (ATEs) — commonly referred to as blood clots and blocked arteries, respectively — associated with drospirenone-containing birth control pills compared with four low-dose estrogen combined hormonal contraceptives (CHCs).
The new study was published in the current online issue of Contraception.
The researchers found that starting the use of drospirenone-containing CHCs was associated with a 77% increase in the risk of hospitalization for a VTE and a doubling of the risk of an ATE compared with the risk associated with the use of the four low-dose estrogen CHCs.
Although the absolute incidence of VTEs was low, the growing number of studies showing an increased risk of these events with drospirenone suggests that drospirenone-containing CHCs should be used cautiously by women seeking hormonal contraception, the authors say.
Drospirenone is a synthetic version of the female hormone progesterone.
The new retrospective study involved 573,680 women, aged 10 to 55 years, who were identified as “new users,” which was defined as first exposure to any of the three drospirenone-containing CHCs or the four low-dose estrogen CHCs during the 2001–2007 study period. The cohort was drawn from two integrated healthcare programs (Kaiser Permanente Northern California and Kaiser Permanente Southern California) and from two state Medicaid programs (Tennessee and Washington).
The comparator CHCs included levonorgestrel/ethinyl estradiol tablets (LNG10-20), levonorgestrel/ethinyl estradiol tablets (LNG15-30), norethindrone/ethinyl estradiol tablets (NETA), and norgestimate/ethinyl estradiol tablets (NGM).
New users of drospirenone had 1.77 times the risk of a VTE and 2.01 times the risk of an ATE compared with new users of the low-dose estrogen comparators. The increased risk associated with drospirenone was limited to subjects aged 10 to 34 years for VTE and to subjects aged 35 to 55 years for ATE.
Use of the norelgestromin/ethinyl estradiol transdermal patch (NGMN) and the etonogestrel/ethinyl estradiol vaginal ring (ETON) was not associated with an increased risk of either thromboembolic or thrombotic outcomes. However, women use the patch and the ring less often than drospirenone-containing birth control pills.
In a drug safety communication dated April 10, 2012, the FDA concluded that “drospirenone-containing birth control pills may be associated with a higher risk for blood clots than other progestin-containing pills.” The FDA advises that, even though it is unclear whether the increased risk of blood clots in some of the epidemiologic studies is actually due to drospirenone-containing birth control pills, women should talk to their healthcare professionals about their risk of clots before deciding which birth control method to use.
Source: Kaiser Permanente, October 18, 2012.