Azithromycin is an antibiotic used to treat various types of bacterial infections, including respiratory infections, skin infections, ear infections, and sexually transmitted infections. It belongs to a class of antibiotics called macrolides and works by stopping the growth of bacteria. Azithromycin is usually taken orally, either as a tablet or as a liquid suspension. The dosage and length of treatment depend on the type of infection being treated and the patient's age and medical history. Common side effects may include nausea, diarrhea, stomach pain, and headache.