The FDA has issued a warning against the antibiotic Zithromax (azithromycin) after it was learned that the drug could cause a potentially fatal irregular heart rhythm in some patients. The drug is made by Pfizer Inc and is also sold by generic drug makers.
According to the Agency, the drug can cause abnormal changes in the electrical activity of the heart that may lead to a potentially fatal heart rhythm known as prolonged QT interval, in which the timing of the heart's contractions becomes irregular.
The FDA said doctors should use caution when giving the popular antibiotic to patients known to have this condition or who have certain risk factors. Those who may be at risk include people with low levels of potassium or magnesium, a slower than normal heart rate, or people who take certain drugs used to treat abnormal heart rhythms, or arrhythmias. The drug could also cause problems in people with torsades de pointes, a specific, rare heart rhythm abnormality.
However, the Food and Drug Administration noted that other drugs in the same class as azithromycin known as macrolides also have the potential for causing QT prolongation, as do non-macrolide antibiotics, such as fluoroquinolones, and doctors need to consider all of these risks when choosing an antibiotic.
Pfizer officials were not immediately available for comment.
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