Though it has broad applications and a conveniently short course, Zithromax treatment raises the possibility of serious liver and kidney side effects.

Zithromax is manufacturer Pfizer Inc.’s trade name for azithromycin. It’s also sold under the trade name Zmax and in a six-tablet dosage pack called Z-Pak. One of a class of antibiotics called macrolides, Zithromax received initial FDA approval in November 1991.

Zithromax is indicated for a wide range of different types of bacterial infections. Like other macrolides, it doesn’t directly attack and kill bacteria but instead inhibits their ability to make proteins, without affecting the protein-building mechanisms in humans. Because Zithromax stays in the human body for a relatively long time, it can be administered with less frequent dosing and shorter courses, usually lasting only five days. Common applications include ear infections, skin infections and infections of both upper and lower respiratory areas.

Like most drugs, Zithromax has its share of side effects. Usually these side effects are short-lived and not severe. The most common Zithromax side effects are nausea, vomiting, diarrhea, and abdominal pain. Since it inhibits growth of the naturally-occurring bacteria in the digestive system, it can lead to colitis. Occasionally, however, a course of Zithromax can cause side effects that are chronic and significantly more troublesome.

Zithromax is, in fact, one of the more common drugs associated with liver damage. As with other macrolides, it has a known relationship with two different forms of hepatoxicity. Zithromax liver problems typically arise within one to three weeks after starting treatment, sometimes beginning even after Zithromax treatment is stopped. Liver damage has been found following even the shortest courses of Zithromax, as short as two or three days. Symptoms include fatigue, itching, jaundice and abdominal pain. Recovery usually takes four to eight weeks, but there have been some rare reports of acute liver failure and death resulting from azithromycin-induced liver disease.

In 2011, the FDA ordered the makers of Zithromax to add a warning to the label alerting consumers to the risk of “[a]bnormal liver function, hepatitis, cholestatic jaundice, hepatic necrosis, and hepatic failure have been reported, some of which have resulted in death.”

Some azithromycin patients have also reported kidney side effects simultaneous with azithromycin treatment. There have been rare reports of interstitial nephritis, an inflammation of the kidneys usually caused by antibiotics or other medication. Some other cases of kidney side effects have led to acute renal failure.

Other serious side effects associated with Zithromax include Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis, two related and debilitating skin conditions. Zithromax is also known to cause QT prolongation, a cardiac arrhythmia that can in rare cases be fatal.

In March 2013, the FDA issued a Drug Safety Communication warning consumers about QT prolongation and updating azithromycin labeling requirements to better reflect this risk. The FDA based that communication on a study published in the New England Journal of Medicine that found an increase in cardiovascular deaths in patients who took a five-day course of azithromycin, as compared to other patients who took different antibiotics or no drugs at all.