Antibiotic azithromycin can cause irregular heart rhythm

The antibiotic azithromycin can cause potentially fatal irregularheart rhythms, the U.S. Food and Drug Administration says.

Theantibiotic is widely used for bronchitis, pneumonia, chest infections, urinary tract and other common infections.

The FDA said Tuesday that the antibiotic, sold inCanada and the U.S. asZithromax, can cause abnormal changes in the electrical activity of the heart that may lead to a potentially fatal irregular heart rhythm.

"Health care professionals should consider the risk of fatal heart rhythms with azithromycin when considering treatment options for patients who are already at risk for cardiovascular events," the regulator advised.

Astudy published lastyear inthe New England Journal of Medicinecompared the risk of cardiovascular death from different antibacterial drugs. Itfound that there was anincrease in cardiovascular deaths and in the risk of death from any cause, in persons treated with a five-day course of azithromycincomparedwith those treated with anotherantibiotics or no drug.

In meaningful terms, thattranslates toless than a 0.1 per cent increased risk of death, saidMuhammad Mamdani, a scientist at St. Michael's Hospital andthe Institute for Clinical Evaluative Sciences in Toronto.

"It's something that shouldn't stop physicians from prescribing the drug," Mamdani said, adding that they just have tobe "a bit more aware of of these potential side-effects."

"If they're sick from a cardiovascular standpoint, if they know that a patient has irregular heart beats, those are probably the patients you don't want to use this drug on."

There are alternative antibiotics available for such patients.

The drug is made by Pfizer Inc.

Zithromax is at least twice as expensive as generic amoxicillin.

Peopleat particular risk for developing this condition include those with known risk factors such as existing QT interval prolongation, low blood levels of potassium or magnesium, a slower than normal heart rate, or use of certain drugs used to treat abnormal heart rhythms, or arrhythmias.

Health Canada said it has received 39 adverse event reports involving azithromycin related to cardiac arrhythmias or irregular heart rhythms.

The department said it communicated risk of heart attack associated with the product in a 2001 newsletter.

"Health Canada is aware of the action taken by the FDA and will consider this new information as part of its review of azithromycin," Stphane Shank, senior adviser of media relations, said in an email.