A zithromycin dihydrate is an azalide antibiotic, a subclass of the macrolide antibiotics. The compatibility of azithromycin with other drugs during Y-site injection has not heretofore been studied.

[2,3,4] Azithromycin dihydrate [a] was supplied in vials containing 500 mg of azithromycin powder. Added to each vial was 4.8 mL of sterile water for injection, resulting in a 100-mg/ mL solution.