• Type: Antibiotic, Macrolide
  • Dosage Forms: powder for solution, suspension reconstituted, packet, tablet
  • Dosage Strengths: powder for solution: 500mg, 2.5g; suspension reconstituted: 100, 200mg/5mL; packet: 1g; tablet: 250, 500, 600mg
  • Routes of Administration: PO, IV
  • Common Trade Names: Zithromax, Z-Pak, Zmax

Adult Dosing

  • Babesiosis (In combination with Atovaquone) [Mild/Moderate 500mg PO x1 on day 1, then 250mg PO q24h x7-10 days. Severe 500mg IV q24hr for 7 to 10 days]
  • Bacterial Infections [500mg PO x1 on day 1, then 250mg PO q24h x4 days]
  • Strep Pharyngitis/tonsillitis [500mg PO x1 on day 1, then 250mg PO q24h x4 days] Alt: 500mg PO q24h x3 days
  • COPD exacerbation [500mg PO x1 on day 1, then 250mg PO q24h x4 days] Alt: 500mg PO q24h x3 days
  • Community-acquired pneumonia [500mg PO x1 on day 1, then 250mg PO q24h x4 days] Alt: 500mg IV q24h x2 or more days, then 500mg PO q24h to complete 7-10 day course
  • Chlamydia: 1 g PO x1; (for uncomplicated urethritis, cervicitis, oropharygeal)
  • Gonorrhea (initial or recurrent) [1 g PO x1]
  • Gonorrhea (persistent) [2 g PO x1]
  • PID [500mg IV q24h x1-2 days, then 250mg PO q24h x5-6 days]
  • Urethritis, non-gonococcal initial infection [1 g PO x1]
  • Chancroid [1 g PO x1]
  • MAC (disseminated) [500-600mg PO q24h] (not 1st-line agent; use with ethambutol)
  • MAC (primary prophylaxis) [1200mg PO qwk] Alt: 600mg PO 2x/wk
  • MAC (secondary prophylaxis) [500-600mg PO q24h] (not 1st-line agent; use with ethambutol)
  • Endocarditis prophylaxis (dental) [500mg PO x1] (Start: 30-60min before procedure)
  • Pertussis [500mg PO on day 1, followed by 250mg q24hr for days 2-5]
  • Presumptive cervicitis [1 g PO x1]
  • Salmonella [1 g PO q24h x1 day, then 500mg PO q24h x2-6 days]
  • Typhoid fever [10mg/kg PO q24h x1wk]

Pediatric Dosing

  • Pneumonia (peds)
    • 10mg/kg/day PO in a once daily dose on day 1 (max 500mg)
      • Followed by 5mg/kg/day PO once daily on days 2-5
  • Bacterial sinusitis: Children ≥6 months: Oral: 10mg/kg PO once daily for 3 days (maximum: 500mg daily)
  • Otitis media: Children ≥6 months: Oral:
    • 1-day regimen: 30mg/kg as a single dose (maximum dose: 1,500mg)
    • 3-day regimen: 10mg/kg once daily for 3 days (maximum: 500mg daily)
    • 5-day regimen: 10mg/kg on day 1 (maximum: 500mg daily) followed by 5mg/kg/day once daily on days 2 to 5 (maximum: 250mg daily)
  • Pharyngitis (as an alternative agent in penicillin allergic patients):
    • Children ≥2 years and Adolescents: Oral: 12mg/kg/dose once daily for 5 days (maximum: 500mg daily)

Special Populations

  • Pregnancy Rating: B
  • Lactation risk: Excreted in low amounts of breast milk and may lead to rash, somnolence, and diarrhea in nursing infants
  • Renal Dosing: Caution in patients with GFR <10 mL/minute, though primarily elimated through hepatic metabolism
  • Hepatic Dosing: Caution is indicated for potential hepatotoxicity though it is rare, and there are no specific dosage adjustments indicated for patients with liver failure


  • Hypersensitivity to azithromycin or other macrolides or any component of the formulation
  • History of cholestatic jaundice/hepatic dysfunction with prior Azithromycin use

Adverse Reactions


Prolonged QT, torsades, hepatic necrosis, Eaton-Lambert, Myasthenia gravis, corneal erosion


Vomiting, diarrhea, abdominal pain, headache, vision changes


  • Half-life: 68 hrs
  • Metabolism: Hepatic
  • Excretion: Biliary
  • Mechanism of Action:Binds 50S ribosomal subunit interfering with microbial protein synthesis

Antibiotic Sensitivities[1]

Group Organism Sensitivity
Gram PositiveStrep. Group A, B, C, GI
Strep. PneumoniaeI
Viridans strepX1
Strep. anginosus gpX1
Enterococcus faecalisR
Enterococcus faeciumR
Staph. EpidermidisR
C. jeikeiumR
L. monocytogenesS
Gram NegativesN. gonorrhoeaeI
N. meningitidisX2
Moraxella catarrhalisS
H. influenzaeS
E. coliR
Klebsiella spR
E. coli/Klebsiella ESBL+R
E coli/Klebsiella KPC+R
Enterobacter sp, AmpC negR
Enterobacter sp, AmpC posR
Serratia spX1
Serratia marcescensR
Salmonella spI
Shigella spI
Proteus mirabilisX1
Proteus vulgarisR
Providencia sp.X1
Morganella sp.X1
Citrobacter freundiiX1
Citrobacter diversusX1
Citrobacter sp.X1
Aeromonas spX1
Acinetobacter sp.R
Pseudomonas aeruginosaR
Burkholderia cepaciaR
Stenotrophomonas maltophiliaR
Yersinia enterocoliticaR
Francisella tularensisX1
Brucella sp.R
Legionella sp.S
Pasteurella multocidaX1
Haemophilus ducreyiS
Vibrio vulnificusX1
MiscChlamydophila spS
Mycoplasm pneumoniaeS
Rickettsia spX1
Mycobacterium aviumS
Bacteroides fragilisR
Prevotella melaninogenicaS
Clostridium difficileX1
Clostridium (not difficile)S
Fusobacterium necrophorumR
Peptostreptococcus sp.S


  • S susceptible/sensitive (usually)
  • I intermediate (variably susceptible/resistant)
  • R resistant (or not effective clinically)
  • S+ synergistic with cell wall antibiotics
  • U sensitive for UTI only (non systemic infection)
  • X1 no data
  • X2 active in vitro, but not used clinically
  • X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
  • X4 active in vitro, but not clinically effective for strep pneumonia

See Also


  1. Sanford Guide to Antimicrobial Therapy 2014
  • Epocrates
  • Micromedex
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