Two studies published in this weeks’ British Medical Journal, one from the US and the other from the UK, report that users of drosperinone containing oral contraceptives (Yaz, Yasmin and their generics) have increased relative risks for non-fatal blood clots compared with users of pills containing levonorgestrel.
While neither study is perfect, and indeed have some very major limitations, they add to a growing body of evidence that pills containing drosperinone may impart higher risks for blood clots than older pills. Yaz is not alone in this regard – other studies have suggested that pills containing the newer progestins gestodene and desogestrel also impart slightly high clot risks than the so-called first and second generation pills containing the older progestins norethindrone and levonorgestrel.
I won’t go into the studies’ limitations here, but will say that trying to get our hands around comparative data on clot risks between various pills is an extraordinarily difficult process given that the diagnosis of blood clots is not always straightforward (or correct), pill choices are not randomized and fraught with prescribing bias, and confounding risk factors for clotting are numerous and difficult to control for. I wish folks would stop trying to answer these questions on the quick and cheap using claims and pharmacy databases without requiring chart review and strict diagnostic criteria. But that’s the way these studies are being done, and that’s the data I am being forced to contend with in my practice, so let’s talk about it.
Just how high is the blod clot risk from Yaz?
Actually, it’s quite small – far, far less than a 1% chance or even a 1 in a thousand chance. According to the US Study, if 100,000 women were to use the pill for a year, clots would occur in 23 Yasmin vs 9.1 levonorgestel containing pill users. In the UK study, corresponding risks were 30.8 for drosperinone vs 12.5 for levonogrestrel-containing pills.
To quote myself –
All estrogen containing contraceptives increase clot risks. At this point, the FDA does not distinguish one from another on the basis of clot risk, given that the date being used to compare them has so many limitations.
The risk for a blood clot in pregnancy is 1 in every 500-2000 pregnancies. So it’s pretty much always safer to take a birth control pill than to be pregnant.
If you are taking Yaz or Yasmin, should you change your pills?
Not necessarily. I’ve written before about this issue, and in general, the answer is no.
Most clots occur in the early months of pill use, so if you’re a long time Yaz or Yasmin user, you’ve pretty much defined yourself as exceedingly low risk, and changing to a different pill is not going to change your very low odds much. If you’re on Yaz because its the only pill you like, then I see no reason to change to a pill that you don’t feel as well on. And if you are taking Yaz because you have severe PMS (PMDD), no other pill is approved for this indication, so I would stay put.
Should Yaz be your first pill?
If you’re just starting out on pills with no special issues, I see no compelling reason why Yaz needs to be your first choice.
Like any pill, Yaz has its pluses and minuses, and most women who use it like it. Not uncommon complaints in Yaz users in my practice are breakthrough bleeding (a complaint I see in most very low dose pills) and hot flashes (a new complaint I never heard in pill users till Yaz and Yasmin hit the market).
Women whom I might steer toward Yaz are those who complain of water retention on other pills (drosperinone has a mild diuretic effect), those very worried about weight gain with pills (Yaz users lose a bit of water weight at first, though they regain it over time), those who are very bothered with PMS (although it is only approved for the more severe form of PMS called PMDD), and those who had mood issues on other pills. Despite this, some Yaz users complain of moodiness, just like users of other pills.
Yaz is FDA approved for acne, and has a theoretical advantage over other pills in this regard in that its progestin also has anti-androgen activity in the skin. Other pills approved for acne treatment are Estrastep (norethindrone, an older progestin), Orthocyclen and ortho tricyclen (norgestimate, a newer progestin with limited comparative clot data). Most pills theoretically can improve acne by means of lowering free testosterone levels.
The data are not perfect, but appear to be leaning towards Yaz having a higher clot risk than older pills. That said, the risks overall are very small, and for some women, worth taking in light of advantages Yaz may have for them. I see no reason to stop taking Yaz if you’ve used it safely till now. I also see no compelling reason why it needs to be your first choice before trying an older pill for just birth control. And there’s no reason other than aggressive marketing why Yaz needs to be the #1 pill prescribed in the United States.
*This blog post was originally published at The Blog That Ate Manhattan*