Azithromycin, a semi-synthetic antibiotic, belongs to a class of drugs know as ‘macrolide antibiotics,’ of which all members are chemically derived from naturally occurring erythromycin. The drug is effective against numerous types of bacteria such as Hemophilus influenzae, Streptococcus pneumoniae, and S. aureus, among others. Azithromycin, like all macrolide antibiotics, prevents bacteria from growing by disrupting their ability to synthesize proteins. Due to differences in the mechanisms of protein synthesis in bacteria and humans, macrolide antibiotics do not interfere with protein production in humans. It is an unusual antibiotic in that it has a long half-life (68 h), permitting once-a-day dosing and shorter treatment times for many infections.