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Zithromax for Lyme Disease – Fatal Heart Attack Warning from FDA

zithromax death lyme disease heart attacks and pfizerOne of the most popular Lyme disease antibiotics, Zithromax, can cause fatal heart attacks, according to an FDA warning issued last week. Azithromycin is one of a handful of antibiotics currently in use to treat the tick-borne infection, although doxycycline is the usual antibiotic prescribed for patients with Lyme disease. The new warning is particularly troubling considering the potential for Lyme carditis to occur in patients infected with Borrelia and it seems likely that this will add weight to the official guidelines that long-term antibiotic activity does more harm than good in Lyme disease patients.

Have Heart Problems? Don’t Use this Drug

The revised recommendation from the US Food and Drug Administration (FDA) is for all patients to be screened for heart problems prior to azithromycin being prescribed. Azithromycin is sold under the brand names Zithromax and Zmax (Pfizer) and has been found to cause abnormal changes in the electrical activity of the heart, with the potential to instigate a fatal arrhythmia. Those who already have an abnormally slow heart rate, who are on drugs for such a condition or who have low circulating potassium or magnesium are at an elevated risk of complications, as are those who have a prolonged QT interval (the space between two parts of the heart’s electrical wave cycle). The FDA also warns that elderly patients and those with existing heart problems face a higher risk of complications with azithromycin.

Pfizer Study Links Zithromax to Patient Deaths

Although the warning over the potentially fatal complications of Zithromax may alter the behaviour of prescribing physicians it should also be remembered that other antibiotics in the macrolide class (as well as some nonmacrolides) can alter the heart’s normal rhythm. This latest warning over Zithromax and heart problems is based on a recent study carried out by Pfizer themselves to determine the effects of azithromycin on the heart’s electrical activity.

Increased Risk With Just Five Days of Treatment

An earlier study, published last year by Ray, et al (2012), had previously noted that patients using this particular antibiotic had a small, increased risk of sudden death from heart complications compared to patients using either no antibiotics or an alternative antibiotic, amoxicillin. These patients were only taking the antibiotics for five days whereas many Lyme disease patients take at least a two week course and some patients are prescribed long-term antibiotics, despite official treatment recommendations frowning upon this practice. The risk appeared to return to normal 6-10 days after discontinuing treatment, which does suggest that there were other, underlying, factors at play in the increased risk of fatal heart attacks with Zithromax use.

Heart Attacks Three Times More Likely With Zithromax Treatment

This study by Ray, et al, calculated the risk for cardiovascular death as almost three times higher (hazard ratio of 2.88) in those taking azithromycin compared to no antibiotics and some two and a half times higher for those taking amoxicillin. Death from all causes was around twice as common in those taking Zithromax compared to no antibiotics (1.85) and compared to amoxicillin (2.02). Azithromycin’s effectiveness as an antibiotic means that is more likely to be used for more serious infections, which the researchers attempted to control for in the results. It may be, however, that patients taking the drugs already had a higher risk of cardiovascular complications and death from any cause, but the results have convinced the FDA that the issue is a serious one and patients and their families are being targeted by injury lawyers to begin proceedings against Pfizer.

Dangerous Antibiotics for Lyme Disease Treatment

Lyme disease antibiotic azithromycin joins other antibiotics, erythromycin, clarithromycin and levofloxacin, on the list of drugs that require especially careful consideration prior to use in those with heart problems. Labelling on the packaging of these drugs is to be updated to reflect the new knowledge of their risk for QT prolongation and abnormal changes in heart activity. Those suffering from Lyme disease may spend years being intermittently treated with antibiotics that appear to raise the risk of cardiac death, despite such treatment being opposed by the US Centers for Disease Control (CDC) and the Infectious Diseases Society of America (IDSA).

Treating Long-Term Lyme Disease with Antibiotics

As always, early treatment of the disease is recommended in order for patients to fight off an infection before it becomes highly entrenched. The short term small increased risk of a fatal heart attack with Zithromax should be weighed against the potential consequences of chronic, untreated Lyme disease which can, itself, cause cardiac problems including Lyme carditis. Patients considering long-term azithromycin treatment may think twice, however, and consider a different antibiotic, such as amoxicillin, when protracted treatment is deemed necessary by a medical professional.


Ray WA, Murray KT, Hall K, et al. Azithromycin and the risk of cardiovascular death. N Engl J Med 2012; 366:1881-90.
FDA Drug Safety Communication: Azithromycin (Zithromax or Zmax) and the risk of potentially fatal heart rhythms. March 12th 2013.

Wynn RL., Azithromycin associated with a small increased risk of cardiovascular death: a review., Gen Dent. 2013 Mar;61(2):8-9.

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