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Food Drug Administration warns: Zithromax may lead to potentially fatal heart rhythms

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By Jimmy Downs

Wednesday March 13, 2013 (foodconsumer.org) -- Azithromycin, one of the best selling antiobiotics, can increase risk of heart disease, the U.S. Food and Drug Administration says in a public safety advisory released March 12, 2013.

The Food and Drug Administration (FDA) is warning the public that azithromycin also known as Zithromax or Zmax can change the normal electrical activity of the heart that may lead to a potentially fatal irregular heart rhythm. 

According to the FDA, at particularly risk for the fatal irregular heart rhythm are people who are already at known risk factors for the lethal condition such as existing QT interval prolongation, low serum levels of potassium or magnesium, a slower than normal heart rate, or using certain drugs indicated to treat abnormal heart rhythm.

The warning came after the FDA reviewed a medical study and another study by a manufacturer of the drug that assessed azithromycin for its potential to cause abnormal changes in the electrical activity of the heart.
Due to the potentially fatal risk, the azithromycin drug labels have been updated in the Warnings and Precautions section to address the risk of QT interval prolongation and torsades de pointes, a specific, rare heart rhythm abnormality or a specific variety of ventricular tachycardia. 

Added in the Warnings section is also information regarding the results of a clinical QT study which found the antibiotic azithromycin can prolong the QTc interval.
Azithromycin is commonly used to treat or prevent certain bacterial infections including those causing middle ear infections, strep throat, pneumonia, typhoid, bronchitis and sinusitis.   Recently it has been primarily used to prevent bacterial infections in infants and those with weakened immune systems such as patients who have received an organ transplant.  The drug may also be used to protect against certain sexually transmitted infections like nongonococcal urethritis, chlamydia, and cervicitis.

According to the FDA, Azithromycin is marketed under the brand names Zithromax and Zmax. It is approved for the treatment of the following diseases and conditions:

Acute bacterial exacerbations of chronic obstructive pulmonary disease
Acute bacterial sinusitis
Community-acquired pneumonia
Uncomplicated skin and skin structure infections
Urethritis and cervicitis
Genital ulcer disease 

"In 2011, approximately 40.3 million individuals in the U.S. received an outpatient prescription for the macrolide azithromycin," the FDA says.

Other common side effects or adverse effects of this antibiotics include diarrhea, nausea, abdominal pain, and vomiting.  Less commonly seen side effects include nervousness, dermatologic reactions, and anaphylaxis.  It can also affect the efficacy of oral contraceptives.  

More serious diseases associated with use of the antibiotic that may be develop include cholestatic hepatitis or delirium. And it is known that accidental intravenous overdosage in an infant can cause severe heart block, resulting in residual encephalopathy.  In worse cases, the drug can increase risk of death particularly in those with heart problems, compared with other antibiotics or no use of antibiotic.

For more information on the drug, visit the website of the Food and Drug Administration.

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