Birth control pills, patches and rings typically contain an estrogen and a progestin component. It has long been known that estrogen-containing birth control preparations (pill, patch, ring) increase the risk for blood clots (DVT, PE). This risk is partially due to the estrogen. However, part of the risk for clots is also due to the type of progestin in these preparations. This first became clear when it was found that so-called 3rd generation contraceptives (those containing the progestin called desogestrel) have about two times higher a risk for DVT and PE that so-called 2nd generation pills.
Drospirenone and risk for blood clots
In the last 4 years data have been published that contraceptives containing the newer progestin component called drospirenone (such as Yasmin, Yaz, Angeliq) may also have a higher risk for clots than the second generation pills. The FDA is reviewing the published data and expecting more data from clinical trials to form a solid opinion. Today they published an update (link here) on “Safety review on the possible increased risk of blood clots with birth control pills containing drospirenone” – these pills are listed here. At this point the FDA concludes that (a) there are conflicting data on the risk for blood clots with these drospirenone-containing contraceptives, (b) preliminary results of an FDA-funded study suggest an approximately 1.5 fold higher risk of blood clots with these pills than with other contraceptive pills, and (c) that a drug safety meeting will take place at the FDA on Dec 8, 2011 to discuss the risks and benefits of these pills further.
When considering a contraceptive method, a woman should take all her risk factors for blood clots into consider:
- Personal history of blood clots (DVT, PE)
- Age (the older the person, the higher the risk for blood clots)
- Family history of blood clots (DVT, PE)
- Presence of a clotting disorder
She and her physician can then take into consideration the risk of blood clots associated with each of the different type of methods. I have found it helpful in discussions to use the following graph (link here). In that image, the broad base of the triangle on top means “highest risk for clots”, the green point at the bottom means “no risk for clots”. A good choice for the thrombosis-prone individual is the Mirena IUD, which dos not seem to increase the risk for blood clots. The Mirena IUD and other progestin-only contraceptives are discussed in a separate Clot Connect blog (link here).
Disclosure: I have no financial conflict of interest relevant to this post.
Last updated: Sept 26th, 2011
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