Drospirenone contraceptives associated with more VTE

Oral contraceptives containing drospirenone are associated with a higher risk of venous thromboembolism than those with levonorgestrel, according to two new studies.

In the first study, 186 newly diagnosed idiopathic cases of venous thromboembolism (VTE) were identified among American women aged 15 to 44 who had received an oral contraceptive containing either drospirenone or levonorgestrel. These cases were matched to 681 controls. A case-control analysis found that drospirenone was associated with a more than twofold higher risk of VTE compared to levonorgestrel. The study also included a cohort analysis finding that incident rates for VTE were 30.8 per 100,000 patient-years with drospirenone and 12.5 per 100,000 patient-years with levonorgestrel.

After adjusting for age, researchers found an increased VTE incidence rate of 2.8 (95% CI, 2.1 to 3.8) with drospirenone compared to levonorgestrel. The increased risk remained when findings were adjusted for risk factors including being a new user of the pill, being obese and having a history of menstrual disorders. The findings differ from some prior research on drospirenone, the authors noted, possibly because the other studies have included non-idiopathic VTE and additional contraceptives shown to carry higher VTE risk, such as cyproterone and desogestrel.

A second similar study, also published online by BMJ on April 21, included 61 cases of idiopathic VTE and 215 matched controls from the United Kingdom General Practice Database. This study found an increased odds ratio for VTE of 3.3 associated with drospirenone compared to levonorgestrel after adjustment for body mass index. The crude incidence rate was 23.0 VTEs per 100,000 patient-years with drospirenone and 9.1 per 100,000 patient-years for levonorgestrel.

Based on their results and other studies finding no clear evidence of additional benefits (such as treatment of acne or premenstrual syndrome) from drospirenone, the authors of the second study concluded that the older contraceptive, levonorgestrel, should be women's first-line choice for oral contraception. The authors of the U.S. study agreed that drospirenone contraceptives (which are sold under the brand name Yasmin) should not be the first choice, as they do not appear to be as safe as levonorgestrel with respect to VTE. They called for additional studies and a systematic review to confirm their findings.