Azithromycin

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General

  • 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

  • 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)
  • 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 in a once daily dose on day 1 (max 500mg)
      • Followed by 5mg/kg/day daily on days 2-5
  • Bacterial sinusitis: Children ≥6 months: Oral: 10mg/kg 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

Contraindications

  • Hypersensitivity to azithromycin or other macrolides or any component of the formulation

Adverse Reactions

Serious

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

Common

Vomiting, diarrhea, abdominal pain, headache, vision changes

Pharmacology

  • 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 Positive Strep. Group A, B, C, G I
Strep. Pneumoniae I
Viridans strep X1
Strep. anginosus gp X1
Enterococcus faecalis R
Enterococcus faecium R
MSSA S
MRSA R
CA-MRSA I
Staph. Epidermidis R
C. jeikeium R
L. monocytogenes S
Gram Negatives N. gonorrhoeae I
N. meningitidis X2
Moraxella catarrhalis S
H. influenzae S
E. coli R
Klebsiella sp R
E. coli/Klebsiella ESBL+ R
E coli/Klebsiella KPC+ R
Enterobacter sp, AmpC neg R
Enterobacter sp, AmpC pos R
Serratia sp X1
Serratia marcescens R
Salmonella sp I
Shigella sp I
Proteus mirabilis X1
Proteus vulgaris R
Providencia sp. X1
Morganella sp. X1
Citrobacter freundii X1
Citrobacter diversus X1
Citrobacter sp. X1
Aeromonas sp X1
Acinetobacter sp. R
Pseudomonas aeruginosa R
Burkholderia cepacia R
Stenotrophomonas maltophilia R
Yersinia enterocolitica R
Francisella tularensis X1
Brucella sp. R
Legionella sp. S
Pasteurella multocida X1
Haemophilus ducreyi S
Vibrio vulnificus X1
Misc Chlamydophila sp S
Mycoplasm pneumoniae S
Rickettsia sp X1
Mycobacterium avium S
Anaerobes Actinomyces S
Bacteroides fragilis R
Prevotella melaninogenica S
Clostridium difficile X1
Clostridium (not difficile) S
Fusobacterium necrophorum R
Peptostreptococcus sp. S

Key

  • 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

References

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