Blood Clots and Hormonal Contraceptives

Hormonal contraceptives are among the most effective means of preventing pregnancy currently in use.  As time goes on, the list of contraceptives with a hormonal mechanism of action gets longer:  oral contraceptive pills of various formulations, vaginal rings, transdermal patches, depot injections, hormone releasing intrauterine devices, implants...seems like the list is limited only by the imagination of drug manufacturers to develop the sine qua non of contraceptives, embodying convenience, effectiveness, acceptable cost and side effect profile, and reversibility.  Yet one troubling aspect of hormonal contraceptive use remains- the risk of blood clots.  Now a study in the New England Journal of Medicine looks at the risk of clots forming in arteries rather than the more typical clot in a vein, so-called venous thrombosis.  Reassuringly, as Rick and I discuss in PodMed, that risk is very small.

The study originated in Denmark, analyzing data from over 1.6 million women, with over 14 million person years of observation, from January 1995 through December 2009.  The women were 15 to 49 years of age during the 15 year study period.  Data on smoking status was available for almost half a million of these women.

Not surprisingly, as women aged they were more at risk for both thrombosis or cardiac problems.  Those women at the higher end of the education spectrum were less likely to experience either thrombosis or a cardiac event. Those women who used hormonal contraceptive products that relied only on progestin did not experience any increased risk, while those who used combination products saw a modestly increased risk of thrombotic events.

Here's what the data revealed:  the researchers state that "among 10,000 women who use desogestrel with ethinyl estradiol at a dose of 20 μg for 1 year, 2 will have arterial thrombosis and 6.8 women taking the same product will have venous thrombosis. Although venous thrombosis is three to four times as frequent as arterial thrombosis among young women, the latter is associated with higher mortality and more serious consequences for the survivors. Therefore, these figures should be taken into account when prescribing hormonal contraception."  As I point out to Rick in the podcast, these numbers sound inflammatory when taken as a percentage increase but are really quite small when absolute risk is assessed.

Moreover, I would balance these risks against those experienced during pregnancy, childbirth, or abortion.  Clearly, this study demonstrates that the risk of hormonal contraception is not zero, and women should probably have their blood pressure assessed accurately previous to using such methods, shouldn't smoke, should take their family history into account, and should probably choose another contraceptive method as they age to reduce these modest risks.

Other topics this week include use of fish oil or insulin in people at cardiovascular risk and diabetes or prediabetes, also in NEJM, exercise testing after revascularization in the long term, and statins and fatigue, both in Archives of Internal Medicine.  Until next week, y'all live well.

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