May 3, 2011 – Two recent studies show that next-generation birth control pills, such as Yasmin® and Yaz®, have a higher risk of venous thrombosis in its users than other oral contraceptives.
A first study1 British government reveals that women who use birth control drugs containing the synthetic hormone drospirenone would be 3 times more likely to suffer from blood clots in the veins than those using an old generation birth control pill containing the hormone levonorgestrel.
By analyzing the medical records of women aged 15 to 44 who used birth control medication from 2002 to 2009, the researchers established an incidence rate of 23 cases per 100,000 women per year of use of popular birth control drugs. This rate rises to 9.1 per 100,000 with older generation oral contraceptives.
The second study2, produced in the United States and published in the same issue of the last British Medical Journal, shows that this risk is 2.3 times higher than in women using a contraceptive free of drospirenone. The incidence rate is 30.8 and 12.5 cases per 100,000 women per year of use respectively.
In both cases, this risk is significant even when considering other risk factors such as age, weight (body mass index) and smoking.
The oral contraceptives Yasmin and Yaz were approved by Health Canada in 2004 and 2008. Its manufacturer, the German group Bayer, presented them when they were marketed as the ultimate in combating premenstrual symptoms while reducing side effects such as than weight gain by water retention.
As soon as the studies were published, the Bayer group challenged in a press release3 their conclusions based on “significant methodological gaps”. According to the manufacturer, the use of Yasmin and Yaz is not riskier than other oral contraceptives which also increase the risk of blood clots.
Opt for old generation birth control drugs
According to Martin Winckler, health communicator and blogger for PasseportSanté.net, the active agent in question, drospirenone, would have a slight diuretic effect in order to counter water retention in some users. However, this would increase the level of potassium in the body, which could cause health problems.
Although all birth control drugs increase the risk of thrombosis due to the clotting properties of their hormones, it appears that the risk is higher with Yasmin and Yaz pills, as other studies have already suggested.
“What is unacceptable is that we are proposing a pill with a purely cosmetic addition to prevent water retention, without any benefit from a contraceptive point of view, and that at the same time increasing the risk of thrombosis in young women, ”says Martin Winckler.
Like the authors of these two studies, Martin Winckler believes that oral contraceptives containing drospirenone should not be the first choice of oral contraceptives for a new user.
“A young woman should not choose this new generation pill for a first prescription, because we lack perspective to assess its effects. The risk of thrombosis is greatest during the first two years of use. You might as well opt for old-generation birth control drugs so as not to run any unnecessary risk, ”he says.
Louis M. Gagné – PasseportSanté.net
1 Parkin L, Sharples K et al. 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 Apr 21; 342: d2139. doi: 10.1136 / bmj.d2139.
2 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 Apr 21; 342: d2151. doi: 10.1136 / bmj.d2151.
3. To read the press release: www.bayer.ca.
