The Safety of Oral Contraceptives in the News
Tue, November 22, 2011 at 03:00AM All oral contraceptives are associated with a risk of blood clots, but some may be more risky than others in this respect. This is reported in an article in the Canadian Medical Association Journal. A study from Israel has identified a problem with some of the more recently-developed, or third generation pills that contain drospirenone.
The data for the study came from 330,000 women in a large Israeli healthcare provider database. All women aged 12 to 50 who were dispensed an oral contraceptive between 2002 and 2008 were included. The rates of venous thrombosis (deep vein thrombosis and pulmonary embolism) and arterial thrombosis (transient ischemic attack and stroke) were recorded; the rates per 10,000 woman-years were then calculated.
The analyses showed that use of pills containing drospirenone were 1.43 more likely to cause venous thromboembolism than other third generation contraceptives, and 1.65 times more likely than second generation pills. There was no increase in the risk of arterial thrombosis with drospirenone.
To put things into perspective, one should realize that for every 10,000 women who get pregnant in a year, roughly 20 will develop venous thrombosis; this compares with a rate of 6 per 10,000 women on the pill overall, and three in 10,000, and women whore not on the pill. In other words, the problem is not great. Nevertheless, it appears that drospirenone users do run a slightly greater risk than those using other pills. Drospirenone is the progestin used in Yaz®, Yasmin®, and some other pills. Because the overall risk is very low, the advice given to women who have taken Yaz or Yasmine for 4 months or longer without any noticeable problems is that they should have no reason to switch to a different pill; this is because blood clot risk is greatest in the first few months of use. Older or obese women, who have a slightly greater risk of thromboses, should probably avoid starting contraception with drospirenone-containing pills.
An additional study, this time from Denmark, has been published recently. The findings are similar, in that combination pills using estrogen and drospirenone (or two other new progestins) were twice as likely to result in venous thrombosis as combinations of estrogen plus an older progestin (levonorgestrel). However, the investigators point out the low absolute risk thus: 2,000 women would need to shift from using oral contraceptives with drospirenone to those with levonorgestrel to prevent one event of venous thromboembolism in one year.
Reader Comments (2)
I use your articles all the time as they are generally great. However this site is about Aging, I thought. Oral Contraceptives don't interest our senior population that much. Thanks though for all the article syou post.
Susie:
You are right. But maybe older readers (like me) have children or grandchildren who are glad to have a senior's health advice from a reliable source passed on.
Bob G.