BMJ: Ingredient in Bayer's Yaz Causes More Blood Clots Than Rivals

Last Updated Sep 11, 2009 4:05 PM EDT

Folks inside the Yaz brand management team at Bayer have another pill-induced headache this month in the form of a BMJ study that indicates the progesterone ingredient of Yaz is more risky than those in other contraceptives.

Conversely, the study will be greeted with joy by the lawyers suing Bayer, who believe that Yaz causes a greater-then-usual number of blood clots compared to older pills because of its new progesterone ingredient.

The study is nice and big: It looked at 1,524 patients on the pill and 1,760 who weren't. Overall, venous thrombosis -- dangerous blood clots -- increased fivefold compared to those not using the pill. Clots remained very low in both populations, however; even in the riskiest population only 13.3 women in 10,000 got them.

Yaz uses drospirenone as its progesterone ingredient. The study said there was a 6.3-fold increase in VT risk for drospirenone. The safest progesterone was levonorgestrel, the study said, which is found in Teva's Seasonique (that's the one that gives you only four periods a year).

The Dutch authors of the survey concluded:

With such a large number of women using oral contraceptives, even the smallest increase of side effects will affect many. Knowledge of these risks and efforts to reduce them are of crucial importance. Our results clearly show that the safest option with regard to the risk of venous thrombosis is an oral contraceptive containing levonorgestrel combined with a low dose of oestrogen.