Azithromycin Dosing in Typhoid (Enteric) Fever

Adults

Note from Harrison's: For uncomplicated disease, azithromycin results in defervescence in 4-6 days, with relapse and convalescent stool carriage rates of <3%. Relapse rates are lower with azithromycin than with fluoroquinolones or ceftriaxone. - Harrison's Principles of Internal Medicine, 22E, p. 1361

Children

• Uncomplicated enteric fever (oral): 20 mg/kg/dose once daily (max 1 g/dose) for 5-7 days - Red Book 2021, p. 1023-1024
• Severe enteric fever (IV, beta-lactam allergy): 10 mg/kg/dose IV once daily (max 500 mg) until oral therapy tolerated, then complete course orally to total 5-7 days
• Oral azithromycin at 10 mg/kg/day (not exceeding 500 mg) for 7 days is also cited in Medscape for children ages 4-17 years

Key Clinical Points

1. Role in resistance patterns: Azithromycin is one of only two drugs (along with carbapenems) effective against XDR (extensively drug-resistant) S. Typhi strains from Pakistan, which are resistant to ceftriaxone, ampicillin, ciprofloxacin, and TMP-SMX. Patients with Pakistan travel history should be treated empirically with azithromycin or a carbapenem.
2. Preferred over fluoroquinolones in children and pregnant women, and in areas with high fluoroquinolone resistance (Indian subcontinent, South/Southeast Asia).
3. Intracellular activity: Azithromycin achieves high intracellular concentrations in macrophages - which is why it works for typhoid when aminoglycosides (equally susceptible in vitro) do not. - Sherris & Ryan's Medical Microbiology, 8E
4. Severe/complicated typhoid: Azithromycin alone is not preferred; IV ceftriaxone or a carbapenem (for XDR) is the drug of choice for severe disease with parenteral therapy.
5. Azithromycin resistance has begun to emerge, particularly in XDR strains, so culture and sensitivity data remain important when available.