Combined oral contraceptives containing drospirenone are associated with a 2- and 3-times higher risk for nonfatal venous thromboembolism than COCs containing levonorgestrel, according to new findings from 2 studies.
Combined oral contraceptives (COCs) containing drospirenone are associated with a 2- to 3-times higher risk for nonfatal venous thromboembolism (VTE) than COCs containing levonorgestrel, according to the findings of 2 studies conducted simultaneously by researchers at the Boston University School of Medicine and the University of Otago Dunedin School of Medicine, New Zealand.
The first study, a nested case-control study, used a general practice research database in the United Kingdom. The researchers included women ages 15 to 44 years without major risk factors for VTE who started using a COC containing 30 μg estrogen with either drospirenone or levonorgestrel between May 2002 and September 2009.
The authors identified 61 women with idiopathic VTE and 215 matched controls. Current use of drospirenone conferred a 3-fold higher risk for nonfatal idiopathic VTE compared with levonorgestrel (odds ratio [OR] adjusted for body mass index was 3.3; 95% Confidence Interval [CI], 1.4-7.6). Crude incidence rate was 23 (95% CI, 13.4-36.9) per 100,000 woman years in current users of COCs containing drospirenone and 9.1 (95% CI, 6.6-12.2) per 100,000 woman years in current users of COCs containing levonorgestrel.
The researchers included 186 women with idiopathic VTE and 681 controls. The odds ratio for developing VTE among users of COCs containing drospirenone compared with those containing levonorgestrel was 2.3 (95% CI, 1.6-3.2). Incidence rates for VTE were 30.8 (95% CI, 25.6-36.8) per 100,000 woman years among users of COCs containing drospirenone and 12.5 (95% CI, 9.61-15.9) per 100,000 woman years for users of COCs containing levonorgestrel.
Parkin L, Sharples K, Hernandez RK, Jick SS. Risk of venous thromboembolism in users of oral contraceptives containing drospirenone or levonorgestrel: nested case-control study based on UK General Practice Research Database. BMJ. 2011;342:d2139.
Jick SS, Hernandez RK. Risk of non-fatal venous thromboembolism in women using oral contraceptives containing drospirenone compared with women using oral contraceptives containing levonorgestrel: case-control study using United States claims data. BMJ. 2011;342:d2151.