Azithromycin, discovered in 1980, is a semi-synthetic macrolide antibiotic derived from erythromycin. The drug is primarily used to treat various bacterial infections including respiratory infections, acute bacterial sinusitis, skin infections, Lyme disease, and some sexually transmitted infections. The mode of action of azithromycin is by inhibiting bacterial protein synthesis through binding to the 50S subunit of the bacterial ribosome, thereby inhibiting translation of mRNA. The USP monograph for the analysis of azithromycin states the use of a high pH mobile phase (pH 11), which requires a specific and expensive column. The method also uses amperometric electrochemical detection, which is often unavailable in many laboratories. HPLC with a UV or PDA detector provides a good alternative as it is available in most laboratories. This application brief describes the use of a Quasar™ C18 column in the analysis of azithromycin.