Azithromycin for Injection, USP contains the active ingredient azithromycin, an azalide, a subclass of macrolide antibiotics, for intravenous injection. Azithromycin has the chemical name (2R,3S,4R,5R,8R,10R,11R,12S,13S,14R)-13-[(2,6-dideoxy-3-C-methyl-3-O-methyl-α-L-ribo-hexopyranosyl)oxy]-2-ethyl-3,4,10-trihydroxy-3,5,6,8,10,12,14-hepta-methyl-11-[[3,4,6-trideoxy-3-(dimethylamino)-β-D-xylo-hexopyranosyl]oxy]-1-oxa-6-azacyclopentadecan-15-one. Azithromycin is derived from erythromycin; however, it differs chemically from erythromycin in that a methyl-substituted nitrogen atom is incorporated into the lactone ring. Its molecular formula is C38H72N2O12, and its molecular weight is 749. Azithromycin has the following structural formula:
Azithromycin, as the monohydrate, is a white crystalline powder with a molecular formula of C38H72N2O12 ∙ H2O and a molecular weight of 767.
Azithromycin for Injection, USP consists of azithromycin monohydrate and the following inactive ingredients: anhydrous citric acid and sodium hydroxide. Sodium hydroxide is added to adjust the pH. Azithromycin for Injection, USP is supplied as white to off-white lyophilized powder in a single-dose ADD-Vantage® vial for intravenous administration only after reconstitution, according to directions in the Dosage and Administration section. Each ADD-Vantage® vial contains azithromycin monohydrate equivalent to 500 mg azithromycin, 392 mg anhydrous citric acid and sodium hydroxide for pH adjustment.