Azithromycin

General

• Type: Antibiotic, Macrolide
• Dosage Forms: 250,500,600 tab; 100,200/5 mL liquid; 1 g pwdr pkt; 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

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

• Antibiotics (Main)

References

• Epocrates
• Micromedex

Authors

Ross Donaldson