Irregular heartbeat affects women taking osteoporosis drug

Irregular heartbeat affects women taking osteoporosis drug

Chronically irregular heartbeat (atrial fibrillation) affected women who had taken Merck's bisphosphonate drug Fosamax (alendronate) to combat the bone-thinning disease osteoporosis nearly twice as often as women who had never used it according to new research from the US.

The investigation was the work of researchers from Group Health and the University of Washington, both in Seattle, and colleagues from other research centres in Seattle and San Francisco, and is published in the 28th April issue of the Archives of Internal Medicine.

Generic versions of alendronate were approved two months ago in February 2008, by the US Food and Drug Administration for the treatment of osteoporosis.

Study leader and professor of epidemiology and researcher at the Cardiovascular Health Research Unit at the University of Washington, Dr Susan Heckbert, said in a prepared statement that:

"We studied more than 700 female Group Health patients whose atrial fibrillation was first detected during a three-year period."

Heckbert and colleagues matched the women, who were diagnosed with atrial fibrillation between October 2001 and December 2004, to over 900 randomly selected female controls who did not have the condition. The controls were also from Group Health and matched the intervention group on age and presence and absence of high blood pressure.

They found that:

  • More women with atrial fibrillation than controls had ever used alendronate (6.5 per cent or 47 women versus 4.1 per cent or 40 women, respectively; p=0.03).
  • Women who had ever used alendronate had an 86 per cent higher risk of having atrial fibrillation compared with women who had never used it or any other bisphosphonate drug.
  • This figure was obtained after adjusting for the matching variables, a diagnosis of osteoporosis, and a history of cardiovascular disease.
The researchers wrote:

"Based onthe population-attributable fraction, we estimated that 3 per cent of incident AF [atrial fibrillation] in this population might be explained by alendronate use."

And concluded that:

"Ever use of alendronate was associated with an increased risk of incident AF in clinical practice."

Heckbert said that osteoporosis affects mostly older women and impairs their quality of life by setting the stage for fractures.

"Careful judgment is required to weigh the risks and benefits of any medication for any individual patient," she explained.

"For most women at high risk of fracture, alendronate's benefit of reducing fractures will outweigh the risk of atrial fibrillation," explained Heckbert.

But she said that women who are at high risk of fractures, but who are also at risk of atrial fibrillation, for instance if they have heart failure, diabetes or heart disease, might want to talk to their doctor about alternative treatments. Estrogen is an alternative treatment for fracture risk, but other studies on hormone therapy have linked this drug to other heart risks.

About 1 in 100 people, and nearly 9 in 100 over the age of 80, have atrial fibrillation. In most cases, said Heckbert, there are no symptoms and it isn't life threatening, but it can cause palpitations, fainting, fatigue, or even congestive heart failure.

Some 70,000 Americans a year have embolic strokes, which can be caused by atrial fibrillation where the blood "pools" and sometimes clots in the atria (chambers of the heart), from which a piece breaks off and causes the stroke. Patients with atrial fibrillation are often treated with the blood thinner warfarin as a precaution against embolic stroke.

Dr Christine Himes Fordyce a Group Health family practitioner said:

"This study will help medical teams better inform their patients about the risks associated with Fosamax, helping us make the best treatment decisions for managing osteoporosis."

"Now with this increased understanding of potential irregular heartbeats, both physicians and their patients should be alert to any problems, report them immediately, and treat them appropriately," she added.

"Use of Alendronate and Risk of Incident Atrial Fibrillation in Women."

Susan R. Heckbert; Guo Li; Steven R. Cummings; Nicholas L. Smith; Bruce M. Psaty.

Arch Intern Med. 2008;168(8):826-831.

Vol. 168 No. 8, April 28, 2008.

Click here for Abstract.

Sources: Group Health press statement, journal abstract.

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Section Issues On Medicine: Cardiology