Compared with older low-dose combined hormonal contraceptives (CHCs), drospirenone-containing contraceptives are associated with a higher risk of thrombotic events, according to the results of a new FDA-funded study.1
Mixed results were found in previous studies evaluating the risk of thrombotic and thromboembolic events related to 3 CHCs that have come to market in the past 10 years (drospirenone-containing contraceptives, norelgestromin-containing patch, and etonogestrel(Drug information on etonogestrel)-containing vaginal ring) compared with older low-dose estrogen CHCs, explained the study authors.1 Therefore, concern has lingered that women who use any of the 3 newer CHCs may have a higher risk of thrombosis than women who use any of the older low-dose CHCs with a known safety profile. However, it is unknown whether these differences in findings stemmed from disparities in study methodology or variations in study populations, said lead author Stephen Sidney, MD, MPH, in a press release.2
To address methodological issues, the study authors compared each of the 3 newer CHCs with 4 older low-dose estrogen CHCs in new users only to assess the risk of venous thromboembolic events (VTEs) and arterial thrombotic events (ATEs). The 4 older comparator CHCs included levonorgestrel(Drug information on levonorgestrel)/ethinyl estradiol(Drug information on estradiol) tablets [LNG10-20 and LNG15-30], norethindrone/ethinyl estradiol tablets, and norgestimate(Drug information on norgestimate)/ethinyl estradiol tablets. Study participants were identified using 4 geographically and demographically diverse health plans. Two plans were integrated health care programs and 2 plans were state Medicaid programs.
Study participants included 573,680 women aged 10 to 55 years whose first exposure to any of 3 newer CHCs or any of 4 older low-dose estrogen comparators occurred during the 2001-2007 study period. Compared with women who used any of the 4 low-dose estrogen comparators, women who used drospirenone-containing pills were 1.77 times more likely to have a venous thromboembolic event and 2.01 times more likely to have an arterial thrombotic event. The increased risk of thrombotic events in women who used drospirenone-containing pills was limited to the age ranges of 10 to 34 years for VTE and 35 to 55 years for ATE. Neither the patch nor the vaginal ring was associated with an increased risk of either VTE or ATE.
Recently, the FDA warned that “drospirenone-containing birth control pills may be associated with a higher risk for blood clots than other progestin-containing pills.”3 Although the risk of developing blood clots is higher in women who use hormonal contraception than in women who do not, the absolute risk of VTEs in patients taking hormonal contraceptives remains low.
- Compared with low-dose estrogen combined hormonal contraceptives (CHCs), drospirenone-containing pills were associated with a higher risk of thrombotic events.
- Drospirenone-containing CHCs should be used cautiously, especially in women with preexisting risk for developing a blood clot.