Zithromax is safer than it was two months ago?

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Sometimes science is like the weather. Wait a few weeks and it changes.

Such is the case with Zithromax (azithromycin), an important antibacterial drug that is a member of the macrolide class of antibiotics (erythromycin being the best known). Azithromycin is used against a number of bacterial infections, including strep throat, pneumonia, and bronchitis.

Back in March, the FDA warned that even a 5 day course of azithromycin could slightly but significantly increase the risk of life-threatening cardiac arrhythmias (called QT prolongation), and that this could cause cardiovascular deaths in an additional 1 in 4,100 among high-risk patients about 2,000 per year in the U.S. Also noted was that the duration of increased risk corresponded to the duration of azithromycin exposure.

But a new study published in The New England Journal of Medicine and reported on MedPage Today should go a long way in assuaging fears of people taking the drug.

Henrik Svanström, MSc, and colleagues at the Statens Serum Institut in Copenhagen analyzed data on 5 million patients from the Danish national health registry between 1997 to 2010 and concluded that the number of extra deaths for patients taking azithromycin was virtually identical to those taking penicillin. In fact (although this has no statistical significance and means nothing) they noted that one fewer patient would die of cardiovascular causes after taking azithromycin per million treatment episodes compared with penicillin.

Yet, it is important to note that there were substantial limitations in the study, for example, lack of information on the reasons for treatment or other cardiovascular risk factors, such as smoking and body mass index all of which were acknowledged by Svanström.

And Dr.Andrew D. Mosholder of the FDA, in an accompanying article concurred, noting that the Danish study did not entirely clear azithromycin of increased cardiovascular risk.

Nonetheless, says ACSH s Dr. Josh Bloom says, even though this study was imperfect, this is very good news. Azithromycin is a very important antibiotic, especially given the fact that bacterial resistance is steadily rendering formerly effective antibiotics useless.