Drospirenone-containing contraceptives associated more commonly with venous thromboembolism than those utilizing levonorgestrel

Key Points

In a study published recently in the British Medical Journal, researchers presented new evidence suggesting oral contraceptives containing drospirenone result in a greater than 2-fold increased odds of developing non-fatal, idiopathic venous thromboembolism (VTE) compared to current users of products containing levonorgestrel.

Levonorgestrel, the most commonly prescribed progestin in the United States, can be found in multiple monophasic and multiphasic oral contraceptives, in emergency contraception (Plan B), and intrauterine devices (Mirena). Drospirenone, a newer, fourth-generation progestin, is currently found in the oral contraceptives Yaz, Yasmin, Yasminelle, and Beyaz.

In order to conduct their analysis, researchers from the Boston Collaborative Drug Surveillance Program and the Boston University School of Medicine examined the PharMetrics database which collects information on claims paid by US managed care plans. This analysis included all women aged 15 to 44 years who received an oral contraceptive containing either drospirenone or levonorgestrel starting from January 2002 forward. Cases were defined as women with current use of 1 of the 2 oral contraceptives and a diagnosis of idiopathic (no identifiable clinical risk factors present) VTE. Cases were matched to up to 4 control patients not experiencing VTE.

Of note, however, the overall risk of developing VTE in such patients was determined to be low. The crude incidence rate was 30.8 per 100,000 woman years in current users of drospirenone and 12.5 per 100,000 woman years in current users of levonorgestrel oral contraceptives. This corresponded to an age-adjusted incidence rate ratio of 2.8 (95% CI, 2.1–3.8).

Researchers also conducted secondary analyses to evaluate the effect of these 2 progestins on the risks of deep vein thrombosis and pulmonary embolism separately. The matched adjusted odds ratios for deep vein thrombosis and pulmonary embolism with drospirenone compared to levonorgestrel were 1.9 (95% CI, 1.1–3.2) and 2.6 (95% CI, 1.6–4.2), respectively.