Zithromax, widely known as a Z-Pak, is a powerful antibiotic manufactured by pharmaceutical giant Pfizer. The active ingredient in Zithromax is azithromycin.

First approved by the U.S. Food and Drug Administration (FDA) in 1992, Zithromax is used to treat bacterial infections such as bronchitis, pneumonia, and infections of the ears, lungs and other organs. Its use has since expanded to include a sexually transmitted diseases and middle-ear infections in children. As an antibiotic, it is not effective in treating viral infections such as a cold or the flu.

In March 2013, however, the FDA warned the public about fatal heart-related and liver failure risks of Zithromax that may open Pfizer up to legal liability.

Side Effects of Zithromax

In most cases, Z-Paks are well-tolerated in patients. In clinical trials, side effects were found to occur in approximately 12 percent of patients, and less than 10 percent of those side effects were classified as severe. Most side effects were mild, but some rare but serious side effects have been reported, however, including fatal heart problems, allergic reactions and liver disease.

Abnormal Heart Activity and Sudden Cardiac Death

In May 2012, a study in the New England Journal of Medicine reported an increase in cardiovascular death in patients treated with azithromycin compared with patients treated with amoxicillin, ciprofloxacin or no drug.

Following this study, the FDA issued a public statement detailing the study and warning that the Z-Pak may have previously unknown side effects relating to risk of cardiovascular death.

In March 2013, based on new studies funded by Pfizer in response to the research in the New England Journal of Medicine, the FDA issued a stronger public warning that azithromycin, including Zithromax, “can cause abnormal changes in the electrical activity of the heart that may lead to a potentially fatal irregular heart rhythm.”

Hepatotoxicity (Toxic Liver Disease)

Because Zithromax is metabolized and processed in the liver, patients with liver problems or abnormal liver function may be at risk of serious problems from the drug. Hepatotoxicity (toxic liver disease) and hepatitis have been reported in patients taking Zithromax, occasionally resulting in death. Zithromax should be discontinued if there are signs of hepatitis, such as fatigue, muscle aches, loss of appetite, dark urine or abdominal discomfort.

Hypersensitivity

Serious allergic reactions to Zithromax have been reported, including angioedema (rapid swelling), anaphylaxis (allergic shock), and skin reactions such as Stevens Johnson Syndrome, a life-threatening skin reaction.