Zithromax (Azithromycin): Dosages, Ingredients, and Safety in Pregnancy
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. 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.
Pharmacological Action and Pharmacodynamics
As a member of the macrolide group, 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. Regarding cardiac electrophysiology, co-administration of azithromycin increased the QTc interval in a dose- and concentration-dependent manner.
Dosage Forms and Presentations
The medication is available in several formulations for different routes of administration:
- Film-coated Tablet 250 mg: Each tablet contains azithromycin dihydrate equivalent to 250 mg azithromycin and is engraved with "Pfizer" on one side and "ZTM 250" on the other side.
- Film-coated Tablet 500 mg: Each tablet contains azithromycin dihydrate equivalent to 500 mg azithromycin and is engraved with "Pfizer" on one side and "ZTM 500" on the other side.
- Powder for Oral Suspension: Each teaspoonful (5 mL) contains azithromycin dihydrate equivalent to 200 mg of azithromycin.
- Powder for Intravenous (IV) Solution: Azithromycin is supplied in a 10 mL vial equivalent to 500 mg azithromycin, providing a 100 mg/mL solution following recommended reconstitution.
Excipients and Inactive Ingredients
The tablets contain pregelatinized starch, calcium phosphate dibasic anhydrous, croscarmellose sodium, magnesium stearate and sodium lauryl sulfate. 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. The IV formulation contains citric acid (anhydrous) 384.6 mg, and sodium hydroxide 198.3 mg.
Safety and Clinical Usage During Pregnancy
Are Antibiotics Safe to Use During Pregnancy? Azithromycin 250mg (z-pack) may be prescribed to treat mycoplasma or ureaplasma in pregnancy. While there has been mention of a 3 day course of azithromycin being used in pregnant patients, special precautions are necessary for high risk pregnancy, such as a patient with DM2 uncontrolled. In such cases, it is important to understand the risk profile for the patient.