Very serious reactions to Zithromax, and serious skin diseases. In the abdomen. It is found to be present in the body for a significant period of time after the required doses. Azithromycin is in a class of medications called macrolide antibiotics which works by stopping the growth of bacteria. In the treatment of uncomplicated genital infections. If the drug is essential to your health, your doctor may advise you to stop breastfeeding until your treatment is finished. Zithromax is used to treat bacterial infections.