Azithromycin is used to treat certain bacterial infections. Find out what the recommended dosages are, how to take the drug, and more. Azithromycin may cause diarrhea, and in some cases it can be severe. It may occur 2 months or more after you stop using this medicine. Do not take any medicine to treat diarrhea without first checking with your doctor. Diarrhea medicines may make the diarrhea worse or make it last longer. Overview: Azithromycin is an antibiotic that is used to treat certain bacterial infections. It works by stopping certain types of bacteria from making proteins they need to grow and multiply. When it works fast, when to watch for side effects, why you shouldn’t skip the last pill, and what no one mentions about your gut afterward. Written plainly, by someone who’s been there. Azithromycin (Zithromax) is an antibiotic medication that treats bacterial infections. It doesn’t treat viral infections. Azithromycin is an antibiotic that fights bacteria. Azithromycin is used to treat many different types of infections caused by bacteria, such as respiratory infections, skin infections, ear infections, eye infections, and sexually transmitted diseases. Azithromycin is in a class of medications called macrolide antibiotics. It works by stopping the growth of bacteria. Antibiotics such as azithromycin will not work for colds, flu, or other viral infections. Using antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment. Azithromycin can usually be taken with or without food, depending on the formulation prescribed. Some patients prefer taking it with a light meal to reduce stomach upset, especially if they experience nausea. Azithromycin oral tablet (Zithromax) is a prescription drug that's used to treat infections caused by bacteria. Learn about uses, dosage, and more.