Zithromax: Dosages and Ingredients | Full Prescribing Info
Azithromycin is the first of a subclass of macrolide antibiotics, known as azalides, and is chemically different from erythromycin. Chemically it is derived by insertion of a nitrogen atom into the lactone ring of erythromycin A. Pharmacotherapeutic group: Macrolides. ATC code: J01FA.
Pharmacology and Mode of Action
Azithromycin binds to the 23S rRNA of the 50S ribosomal subunit. It blocks protein synthesis by inhibiting the transpeptidation/translocation step of protein synthesis and by inhibiting the assembly of the 50S ribosomal subunit.
Cardiac electrophysiology was also evaluated: Co-administration of azithromycin increased the QTc interval in a dose- and concentration-dependent manner. In comparison to chloroquine alone, the maximum mean increases in QTcF were 5 (10) ms, 7 (12) ms and 9 (14) ms with the co-administration of 500 mg, 1000 mg and 1500 mg azithromycin, respectively.
Available Formulations and Dosages
The following table provides a summary of the available forms and strengths of Zithromax based on the prescribing information:
| Formulation | Strength/Concentration | Physical Characteristics |
|---|---|---|
| Film-coated Tablet 250 mg | Equivalent to 250 mg of azithromycin | Capsular shaped; engraved with "Pfizer" on one side and "ZTM 250" on the other side. |
| Film-coated Tablet 500 mg | Equivalent to 500 mg of azithromycin | Capsular shaped; engraved with "Pfizer" on one side and "ZTM 500" on the other side. |
| Powder for Oral Suspension | 200 mg azithromycin per 5 mL | White to off-white dry powder; yields off-white to orange to brown suspension on reconstitution. |
| Powder for Intravenous (IV) Solution | 500 mg per 10 mL vial | Supplied in lyophilized form under a vacuum; yields 100 mg azithromycin per 1 mL upon reconstitution. |
Chemical Composition and Ingredients
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. Its molecular formula is C 38H 72N 2O 12, and its molecular weight is 749.00.
Inactive Ingredients and Excipients
- Film-coated Tablets: The tablets contain pregelatinized starch, calcium phosphate dibasic anhydrous, croscarmellose sodium, magnesium stearate and sodium lauryl sulfate. The film coating contains hydroxypropyl methylcellulose, triacetin and titanium dioxide (E171).
- Powder for Oral Suspension: The powder for oral suspension contains sucrose (1.94 g per 100 mg dose), sodium phosphate tribasic anhydrous, hydroxypropyl cellulose, xanthan gum, artificial cherry, creme de vanilla and banana flavors.
- Powder for Intravenous Solution: The IV formulation contains citric acid (anhydrous) 384.6 mg, and sodium hydroxide 198.3 mg.