While atrial fibrillation or an irregular heart beat does not carry any symptoms, it can cause blood clots and thereby lead to an embolic stroke. The new study is not the first one to find a link between Fosamax and atrial fibrillation. However, the study reported in the Archives of Internal Medicine has definitely found the highest association in terms of risk.

The small study involving 719 women with atrial fibrillation and more than 966 women as controls was carried out by Dr. Susan Heckbert and colleagues. The women were all in a similar age range and also had similar blood pressure levels. The researchers found that women who had used Fosamax – generic name alendronate – at any time during their life had 86% higher risk of atrial fibrillation compared to those who had never used the drug.

“Having ever used alendronate was associated with an 86% higher risk of newly detected atrial fibrillation compared with never having used the drug,” said Dr. Heckbert. But she added, “Careful judgement is required to weigh the risks and benefits of any medication for any individual patient. For most women at high risk of fracture, alendronate’s benefit of reducing fractures will outweigh the risk of atrial fibrillation.” She also urged women at risk for atrial fibrillation on account of existing health issues such as heart disease or diabetes to consult their doctor for alternative treatment.

A similar study published last year in the New England Journal of Medicine also found an increased risk of atrial fibrillation in thousands of women on Fosamax compared to those who were not. The risk however was significantly lower. On the other hand, a study reported in the British Medical Journal failed to find any connection between increased risk of atrial fibrillation and treatment with bisphosphonates – the class of drugs to which Fosamax belongs.

According to The National Osteoporosis Society, this latest study was “interesting, but should be considered in the context with other recent research, which has not shown the same increase in atrial fibrillation. Fosamax is highly effective at reducing someone’s risk of experiencing a fracture due to osteoporosis,” said spokeswoman Sarah Leyland.

“There are a range of treatments available to people with osteoporosis and at risk of breaking bones. We would urge anyone who is concerned about possible side effects to speak to their GP about the most appropriate treatment for them,” she added.