Zithromax, known generically as azithromycin, is an antibiotic manufactured by Pfizer. It is used to treat bacterial infections such as pneumonia, sexually transmitted diseases (STDs) and infections of the ears, lungs, sinuses, skin, throat and reproductive organs. Azithromycin is classified as a macrolide antibiotic and works by inhibiting the growth of bacteria.
The U.S. Food and Drug Administration (FDA) approved Zithromax in the early 1990s. It quickly became popular due to its short regimen of five to seven days. Many other antibiotics must be taken for ten days.
As with any other drug, Zithromax carries a risk of certain side effects; some are more serious than others. Being aware of these potential side effects can help both patients and healthcare professionals identify problems and address them as soon as possible.
One rare but serious side effect is Stevens-Johnson Syndrome (SJS), a life-threatening allergic reaction that affects the skin and mucous membranes. Early signs may include flu-like symptoms, followed by a rash that spreads and blisters. The top layer of the skin then dies and sheds. Once SJS affects more than 30 percent of the body, it is classified as toxic epidermal necrolysis (TEN). Patients suffering from SJS often require skin grafts.
SJS can also affect a patient’s vision and lead to blindness in some cases. If the reaction causes inflammation in the ocular area, it can lead to scarring and damage to the eye tissue. In 2012, the FDA issued a warning letter to Pfizer over Zithromax and the link to SJS. The agency stated that although the label mentioned early warning signs such as skin rash and blisters, the company reportedly did not point out that the condition is life-threatening.
In 2013, the FDA strengthened the warning label on Zithromax to warn that it can cause potentially fatal heart rhythms. The alert stated that “Patients at particular risk for developing this condition include those with known risk factors such as existing QT interval prolongation, low blood levels of potassium or magnesium, a slower than normal heart rate, or use of certain drugs used to treat abnormal heart rhythms, or arrhythmias.”