There is a greater risk of venous thromboembolism for women who take newer oral contraceptives than for those taking second-generation contraceptives, according to a study published in May in the British Medical Journal.
Researchers investigated the association between the use of combined oral contraceptives and risk of venous thromboembolism, taking the type of progestogen into account.
Using two nested case-control studies in the United Kingdom, researchers looked at an open cohort of women ages 15 – 49, analyzing data from 618 Clinical Practice Research Datalink practices and 722 QResearch database practices.
The participants were women with a first diagnosis of VTE in 2001-2013, each matched with up to five controls by age, practice and calendar year.
After adjusting for smoking status, alcohol consumption, ethnic group, body mass index, comorbidities and other contraceptive drugs, results showed current exposure to any combined oral contraceptive was associated with an increased risk of VTE, compared with no exposure in the previous year.
Specifically, corresponding risks associated with current exposure to desogestrel, gestodene, drospirenone and cyproterone were significantly higher than those for second-generation contraceptives such as levonorgestrel, norethisterone, and norgestimate.
The number of extra cases of venous thromboembolism per year per 10,000 treated women was lowest for levonorgestrel and norgestimate, and highest for desogestrel and cyproterone.
In absolute terms, an extra 14 VTE cases would be expected per year per 10,000 women treated with desogestrel, whereas an extra six cases would be expected with levonorgestrel, according to an NEJM press release.
“We believe this study has the statistical power and sufficient adjustment for relevant confounders to be regarded as an important clarifying study, which has produced the most reliable possible risk estimates using currently available UK prescription data,” researchers stated in the study. “It has confirmed results from other recent large scale studies and added new evidence, particularly for newer or less used combined oral preparations, such as those containing drospirenone or norgestimate. Risks associated with combined oral contraceptives were, apart from norgestimate, higher for newer drug preparations than for second generation drugs.”
Read more: BMJ.com/content/350/bmj.h2135
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