Azithromycin is a semi-synthetic macrolide antibiotic, which is chemically related to erythromycin and clarithromycin. It is used in the treatment of infections caused by a wide variety of bacteria such as Hemophilus influenzae, Streptococcus pneumoniae, Mycoplasma pneumoniae, Staphylococcus aureus, mycobacterium avium, and many others. Azithromycin prevents bacteria from growing by interfering with their ability to make proteins. Due to the differences in the way proteins are made in bacteria and humans, the macrolide antibiotics do not interfere with production of proteins in humans.
Azithromycin is commonly administered in tablet or oral suspension. It is also available for intravenous injection and in a 1% ophthalmic solution. Tablets come in 250 mg and 500 mg doses. It is sold under the brand name Zithromax.