ā/zith’r ō/mī /sən

Brand Name: Zithromax® & Zmax™

• Generic Available

Common Dosage Forms:

  • Tablets: 250 mg, 500 mg and 600 mg. A Z-Pak contains six 250 mg tablets and a Tri-Pak contains three 500 mg tablets.
  • Packets: Each packet contains 1 gm following reconstitution.
  • Zmax powder for suspension: 2 g azithromycin (extended release).
  • Powder for suspension: 300 mg (100 mg/5 mL), 600 mg, 900 mg and 1200 mg (each containing 200 mg/5 mL) azithromycin per bottle following reconstitution.
  • Powder for Injection: Each vial contains 500 mg azithromycin in a lyophilized form.

FDA Indications/Dosages:

  • Mild to moderate infections of the lower and upper respiratory tract and skin and skin structure caused by susceptible strains of H influenzae, M catarrhalis, S pneumoniae, S pyogenes,Saureus,or Sagalactiae: 500 mg as a single dose on the first day followed by 250 mg once daily for 4 more days.

  • Treatment of acute bacterial sinusitis due to H influenzae, M catarrhalis, or S pneumoniae: 500 mg given once daily for 3 days or 2 g Zmax given one time.
  • Treatment of mild to moderate acute bacterial exacerbations of chronic obstructive pulmonary disease: Give 500 mg per day for 3 days or 500 mg as a single dose on the first day followed by 250 mg once daily on days 2 through 5.
  • Treatment  of  genital  ulcer  disease  due  to  Haemophilus  ducreyi, non-gonococcal urethritis and cervicitis due to C trachomatis: Give a single 1 gram dose.
  • Treatment of urethritis and cervicitis due to Neisseriagonorrhoeae:Give a single 2 gram dose.
  • Treatment of acute otitis media due to H influenzae, M catarrhalis,and S pneumoniae, in children 6 months and older: 10 mg/kg as a single dose on the first day followed by 5 mg/kg on days 2 through 5.
  • Treatment of pharyngitis/tonsillitis due to Streptococcuspyogenes, in children 2 years and older: 12 mg/kg once a day for 5 days.
  • For the prevention of disseminated Mycobacterium  aviumcomplex (MAC) disease in persons with advanced HIV infection: 1200 mg taken once weekly.
  • Treatment of community-acquired pneumonia due to C. pneumoniae, H. influenzae, L. pneumophila, M. catarrhalis, M. pneumoniae, S. aureus,or S. pneumoniae:500 mg given intravenously for the first 2 days followed by 250 mg orally twice a day for 7-10 days. Infuse at a concentration of 1-2 mg/mL over at least 60 minutes.
  • Treatment of pelvic inflammatory disease due to C. trachomatis, N. gonorrhoeae,or M. hominis : Same dose as that for community-acquired pneumonia.

Pharmacology/Pharmacokinetics:

Azithromycin dihydrate is a macrolide antibiotic which binds to the 50 S ribosomal subunit of susceptible bacteria thereby suppressing protein synthesis. Distribution occurs to most body tissues except CSF. Excretion occurs primarily through the bile as unchanged drug. The long terminal half-life of 68 hours may be due to uptake and release from tissues. Zmax provides a higher peak serum concentration and greater systemic exposure on the day of dosing versus 1.5 g over 3 or 5 days (Z-Pak or Tri-Pak). Zmax is not bioequivalent to two 1 g sachets. Food increases peak concentrations of tablets and suspensions. Food decreases peak concentrations of Zmax formulations.

Drug Interactions:

Antacids slow absorption. Food decreases absorption. Nelfinavir increases (doubles) serum concentrations of azithromycin. Use with caution with drugs which prolong the QT interval.

Contraindications/Precautions:

Contraindicated in patients with a history of hypersensitivity to macrolides or ketolides. Use caution in patients with impaired hepatic function. Use with caution in patients with a prolonged QT interval, low blood levels of potassium or magnesium, and bradycardia. Use with caution in patients being treated for arrhythmias. Pseudomembranous colitis and secondary bacterial infections may occur with broad spectrum antibiotics–contact a physician if diarrhea becomes severe or persistent. Do not use for complicated pneumonia, gonorrhea or syphilis. Pregnancy Category B.

Adverse Effects:

DIARRHEA (4.3%), nausea (3.9%), vomiting (1.4%), and abdominal pain (2.7%).   Intravenous therapy may cause pain at the injection site (6.5%) and local inflammation (3.1%).

Patient Consultation:

  • Tablets and suspensions are preferably taken with food.
  • Zmax™ formulations should be taken on an empty stomach, 1 hour before or 2 hours following a meal.
  • Do not take antacids within one hour of administration.
  • Store in a cool, dry place away from sunlight and children.
  • Report severe or persistent diarrhea to a physician.
  • Take a missed dose as soon as possible and continue dosing schedule.
  • Shake suspensions well before each dose.