Azithromycin is a widely used antibiotic in the macrolide class. Other antibiotics in this class, as well as nonmacrolides such as fluoroquinolones, can cause abnormal changes in cardiac electrical activity that may prolong the QT interval and result in torsades de pointes.
A study published in the New England Journal of Medicine in May 2012 showed a small, increased risk for sudden cardiac death in patients treated with azithromycin for 5 days vs those treated with amoxicillin or those not treated with antibiotics. These findings prompted further review from the US Food and Drug Administration (FDA).
Study Synopsis and Perspective
The popular antibiotic azithromycin (Zithromax and Zmax) poses the risk for a potentially fatal irregular heart rhythm, which therefore warrants careful screening of patients for this drug, the FDA announced.
The macrolide-class antibiotic can cause abnormal changes in the electrical activity of the heart that may prolong the QT interval and trigger a rare, associated arrhythmia called torsades de pointes.
The FDA stated that patients at risk for this azithromycin-induced arrhythmia include those who already have a prolonged QT interval, low blood levels of potassium or magnesium, and an abnormally slow heart rate, or who take drugs to treat arrhythmias. Elderly patients and patients with cardiac disease also may be more susceptible to the arrhythmogenic effects of the antibiotic.
The agency advised clinicians to put the cardiac risk for azithromycin in an "appropriate context," because other antibiotics in the macrolide class as well as nonmacrolides such as fluoroquinolones can prolong the heart's QT interval.
The FDA safety announcement about azithromycin follows a review of a study conducted on the antibiotic's effect on cardiac electrical activity and another study published in the New England Journal of Medicine in May 2012. The study reported that patients receiving a 5-day course of azithromycin had a small, increased risk for sudden cardiac death compared with those who received amoxicillin or no antibiotics. The FDA said at the time that it would review these findings.
The agency has updated the label of azithromycin to warn of the risk for QT interval prolongation and torsades de pointes.
Other Precautions and Warnings
Caution is indicated when giving azithromycin to patients with impaired hepatic function or to those with a glomerular filtration rate of less than 10 mL/minute. If signs and symptoms of hepatitis occur, azithromycin should be discontinued immediately, as abnormal liver function, hepatitis, cholestatic jaundice, hepatic necrosis, and hepatic failure have been reported and may be fatal.
Patients receiving azithromycin may have exacerbation of symptoms of myasthenia gravis or new onset of myasthenic syndrome.
Unless bacterial infection is proven or strongly suspected, or unless there is a prophylactic indication, prescribing azithromycin is unlikely to be beneficial and increases the risk for the development of drug-resistant bacteria.
For treatment of pneumonia, azithromycin has only been shown to be safe and effective in the treatment of community-acquired pneumonia caused by Chlamydia pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, or Streptococcus pneumoniae in patients for whom oral therapy is appropriate. It should not be used in patients with pneumonia in whom oral therapy is inappropriate because of moderate to severe illness or risk factors.
Serious allergic reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis, have rarely been reported but may rarely be fatal. Azithromycin should be discontinued immediately if an allergic reaction occurs and appropriate therapy started. However, the allergic symptoms may reappear when symptomatic therapy is discontinued.
Clostridium difficile–associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including azithromycin. If CDAD is suspected or confirmed, the offending antibiotics may need to be discontinued, along with institution of appropriate fluid and electrolyte therapy, protein supplementation, antibiotic treatment of C difficile, and surgical evaluation.
Azithromycin is contraindicated in patients with known hypersensitivity to the drug, or to erythromycin or any macrolide or ketolide antibiotic.
Azithromycin is contraindicated in patients in whom cholestatic jaundice or hepatic dysfunction previously developed when given azithromycin.
Use in Special Populations
Azithromycin is Pregnancy Category B. Care should be exercised when azithromycin is given to a breast-feeding woman.
Pharmacokinetics in older volunteers (65 - 85 years old) were similar to those in younger volunteers (18 - 40 years old) for the 5-day therapeutic regimen, and dosage adjustment does not appear to be needed for this regimen for older patients with normal renal and hepatic function. Compared with younger patients, elderly patients may be more susceptible to development of torsades de pointes arrhythmia.
Laurie Barclay, MD, has contributed to this synopsis.
More information about this drug safety communication is available on the FDA Web site.
To report problems with azithromycin, contact MedWatch, the FDA's safety information and adverse event reporting program, by telephone at 1-800-FDA-1088; by fax at 1-800-FDA-0178; online at https://www.accessdata.fda.gov/scripts/medwatch/medwatch-online.htm; with postage-paid FDA form 3500, available at http://www.fda.gov/MedWatch/getforms.htm; or by mail to MedWatch, 5600 Fishers Lane, Rockville, Maryland 20852-9787.
- The FDA warns that patients should be carefully screened before azithromycin is prescribed, as the drug is linked to the risks for prolonged QT interval and for potentially fatal torsades de pointes. High-risk patients for this arrhythmia include those who already have a prolonged QT interval, hypokalemia, hypomagnesemia, or bradycardia. Other risk factors include use of antiarrhythmic drugs, advanced age, and cardiac disease. The azithromycin label now warns of the risks for QT interval prolongation and torsades de pointes.
- Other warnings and precautions regarding azithromycin address impaired hepatic function, myasthenic symptoms, serious allergic reactions, and CDAD. Unless bacterial infection is proven or strongly suspected, or unless there is a prophylactic indication, prescribing azithromycin is unlikely to be beneficial and increases the risk for the development of drug-resistant bacteria. It should not be used in patients with pneumonia in whom oral therapy is inappropriate because of moderate to severe illness or risk factors.
- Azithromycin is Pregnancy Category B. Care should be exercised when azithromycin is given to a breast-feeding woman. For older patients with normal renal and hepatic function, dosage adjustment does not appear to be needed for the 5-day therapeutic regimen, However, elderly patients may be at greater risk for torsades de pointes.
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