04/30/2008- A  study has found that women who use the drug Fosamax are twice as likely to develop an irregular heartbeat condition known as atrial fibrillation as women who have never taken the drug.  The 86% increased risk of atrial fibrillation was an unexpected finding. 

Atrial fibrillation can cause fatigue, fainting, heart palpitations and congestive heart failure.  The condition can also lead to blood clots and stroke. 

As expected, the manufacturer, Merck, responded to these reports with the same canned response it has had to other negative findings - that there is not enough evidence that Fosamax is dangerous or that the risks outweigh the benefits.  I think we heard that when the first reports of the link between the use of Fosamax and osteonecrosis of the jaw.  I know we heard that same response with regard to Vioxx.  In lawsuits pertaining to Vioxx and lawsuits pertaining to osteonectrosis of the jaw due to Fosamax use, Merck has been accused of downplaying risks in order not to sacrifice profits.

More studies are definitely needed, but women using Fosamax should talk over their health concerns with their doctors and doctors need to be on the lookout for this serious complication.