What is the recommended dose of azithromycin for treating bacterial infections?

Azithromycin Dosing for Bacterial Infections

Azithromycin dosing varies significantly by infection type and patient age, with most adult regimens ranging from a single 1-2 gram dose for sexually transmitted infections to 500 mg daily for 3 days for respiratory infections, while pediatric dosing is weight-based at 10 mg/kg on day 1 followed by 5 mg/kg daily for days 2-5. 1

Adult Dosing Regimens

Respiratory Tract Infections

• Community-acquired pneumonia (mild): 500 mg as a single dose on day 1, followed by 250 mg once daily on days 2-5 1
• Acute bacterial exacerbations of COPD: Either 500 mg daily for 3 days OR 500 mg on day 1 followed by 250 mg daily on days 2-5 1
• Acute bacterial sinusitis: 500 mg daily for 3 days 1
• Pharyngitis/tonsillitis (second-line): 500 mg on day 1, followed by 250 mg once daily on days 2-5 1

Sexually Transmitted Infections

• Non-gonococcal urethritis and cervicitis: Single 1 gram dose 1, 2
• Chlamydia trachomatis: 1.0-1.5 g as a single dose 2
• Gonococcal urethritis/cervicitis: Single 2 gram dose (though this is typically used in combination with ceftriaxone) 1
• Mycoplasma genitalium: 500 mg on day 1, then 250 mg daily for 4 additional days 2
• Genital ulcer disease (chancroid): Single 1 gram dose 1

Travelers' Diarrhea and Dysentery

• Dysentery or febrile diarrhea: Either single 1 gram dose OR 500 mg daily for 3 days 2
• This is the first-line agent for dysentery due to widespread fluoroquinolone resistance in Campylobacter and Shigella species 2

Skin and Soft Tissue Infections

• Uncomplicated infections: 500 mg on day 1, followed by 250 mg once daily on days 2-5 1

Specialized Indications

• Legionnaires' disease (hospitalized): 500 mg IV daily for 2-7 days, then oral to complete 7-10 days total 3
• Legionnaires' disease (outpatient): 500 mg on day 1, followed by 250 mg daily for 4 days 3

Pediatric Dosing Regimens

Respiratory Tract Infections

• Community-acquired pneumonia: 10 mg/kg as a single dose on day 1 (maximum 500 mg), followed by 5 mg/kg once daily on days 2-5 (maximum 250 mg/day) 1, 2
• Acute bacterial sinusitis: 10 mg/kg once daily for 3 days 1
• Pharyngitis/tonsillitis: 12 mg/kg once daily for 5 days (note the higher dose than other indications) 1

Otitis Media

Three acceptable regimens 1:

• 5-day regimen: 10 mg/kg on day 1, then 5 mg/kg daily on days 2-5
• 3-day regimen: 10 mg/kg once daily for 3 days
• Single-dose regimen: 30 mg/kg as a single dose

Pertussis

• Infants <6 months: 10 mg/kg per day for 5 days 4
• Infants and children ≥6 months: 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg per day (maximum 250 mg) on days 2-5 4

Key Clinical Considerations

Administration

• Can be taken with or without food for both tablets and oral suspension 1
• Avoid concurrent antacids: If aluminum or magnesium-containing antacids are needed, separate administration as they reduce azithromycin absorption 4

Special Populations

• Renal impairment (GFR >10 mL/min): No dose adjustment needed 1
• Severe renal impairment (GFR <10 mL/min): Use with caution as AUC increases by 35%, though no specific dose adjustment is established 1
• Hepatic impairment: No established dosing recommendations; pharmacokinetics not studied 1
• Pregnancy: FDA Category B; considered safe 4
• Infants <1 month: Preferred over erythromycin due to lower risk of infantile hypertrophic pyloric stenosis 4

Advantages of Azithromycin

• Extended tissue half-life allows for short treatment courses (3-5 days vs. 7-10 days for comparators) 5, 6
• Once-daily dosing improves compliance compared to multiple-daily-dose regimens 5
• Single-dose regimens for STIs enable directly observed therapy 4
• Better GI tolerability than erythromycin 7, 5

Common Pitfalls

• Pharyngitis dosing error: Requires 12 mg/kg daily for 5 days in children, NOT the standard 10 mg/kg/5 mg/kg regimen, due to higher recurrence rates with lower doses 1, 7
• Gonococcal infections: Azithromycin should NOT be used as monotherapy; always combine with ceftriaxone due to resistance concerns 2
• Macrolide-resistant Mycoplasma genitalium: If resistance is detected or suspected, switch to moxifloxacin 400 mg daily for 7-14 days 2
• Persistent non-gonococcal urethritis: After first-line doxycycline failure, use the extended 5-day azithromycin regimen (500 mg day 1, then 250 mg for 4 days), not the single-dose regimen 2, 4

Adverse Effects

• Most common: Gastrointestinal symptoms including abdominal discomfort, diarrhea, nausea, and vomiting 4
• Other: Headache and dizziness 4
• Generally mild to moderate in severity and less frequent than with erythromycin 7, 5