By Christian Duffin
Two new studies have added to evidence that some types of contraceptive pill carry a higher risk of serious blood clots than others.
Pills containing the progestogen hormone drospirenone are associated with three times the level of risk of venous thromboembolism than pills containing levonorgestrel, the research suggests.
One study, based on US medical claims data, found a two-fold increased risk of a non-fatal venous thromboembolism in women using drospirenone-containing oral contraceptives compared with women using levonorgestrel-containing oral contraceptives.
The second study used statistics from the UK General Practice Research Database. It found a three-fold increased risk of a first non-fatal venous thromboembolism in women using drospirenone-containing oral contraceptives compared with women using levonorgestrel-containing oral contraceptives.
Professor Susan Jick, professor of epidemiology from Boston University, who was involved in both studies, said: 'Prescribing lower-risk levonorgestrel preparations as the first-line choice in women wishing to take an oral contraceptive would seem prudent.'
BMJ 2011; 342: 2451 and BMJ 2011; 342: 2139
Lower clot risk with levonorgestrel
