What is the recommended dose of Azithromycin (generic name) per kilogram in pediatric patients with normal renal function?

Azithromycin Dosing in Pediatric Patients

The standard azithromycin dose for children is 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg (maximum 250 mg) daily for days 2-5, for most respiratory tract infections. 1

Standard Dosing Regimens by Indication

Community-Acquired Pneumonia and Atypical Pneumonia

• 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg (max 250 mg) daily for days 2-5 is recommended by the American Academy of Pediatrics and Infectious Diseases Society of America for community-acquired pneumonia, particularly atypical pneumonia caused by Mycoplasma pneumoniae, Chlamydia pneumoniae, or Chlamydia trachomatis 1, 2
• This 5-day regimen is the preferred standard for respiratory infections in children 6 months and older 1
• Clinical improvement should be evident within 48-72 hours; if not, reassess for complications 1

Alternative 3-Day Regimen

• 10 mg/kg once daily for 3 days is an acceptable alternative regimen with comparable efficacy to the 5-day course for respiratory tract infections 1, 3
• The FDA label confirms this dosing was studied in pediatric patients aged 1-15 years with mean pharmacokinetic parameters demonstrating adequate drug exposure 4
• Both 3-day and 5-day regimens show similar clinical cure rates (95.7% vs 96.1%) and bacteriological eradication rates (90.1% vs 94.2%) 3

Pertussis Treatment and Prophylaxis

• Infants <6 months: 10 mg/kg once daily for 5 days 1
• Children ≥6 months: 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg (max 250 mg) daily for days 2-5 1
• Azithromycin is preferred over erythromycin in young infants due to better safety profile and no association with infantile hypertrophic pyloric stenosis 1

Streptococcal Pharyngitis (Second-Line Only)

• 12 mg/kg once daily for 5 days (maximum 500 mg/day) is necessary for strep throat 1
• The higher dose is required because standard 10 mg/kg dosing results in high recurrence rates 1, 5
• Penicillin or amoxicillin remains first-line; azithromycin is only for penicillin-allergic patients 1, 2

Intravenous Dosing

• 10 mg/kg IV once daily (max 500 mg) on days 1-2, then transition to oral therapy as soon as clinically feasible 1
• IV azithromycin is specifically indicated for atypical pathogens when parenteral therapy is required 1
• Avoid prolonged IV therapy beyond 2 days when oral therapy is tolerated 1

Weight-Based Dosing for Convenience

For once-daily dosing in children who cannot calculate mg/kg easily:

• 15-25 kg: 200 mg once daily 1
• 26-35 kg: 300 mg once daily 1
• 36-45 kg: 400 mg once daily 1
• ≥46 kg: 500 mg once daily 1

Special Populations and Considerations

Adolescents with Chlamydial Infections

• Single 1 gram oral dose for uncomplicated urethritis or cervicitis caused by Chlamydia trachomatis 1

MAC Prophylaxis in HIV-Infected Children

• 20 mg/kg (maximum 1,200 mg) once weekly for Mycobacterium avium complex prophylaxis 1

Renal Impairment

• No dosage adjustment needed for mild to moderate renal impairment (GFR 10-80 mL/min) 4
• Use caution in severe renal impairment (GFR <10 mL/min) as AUC increases by 35% and Cmax by 61% 4

Critical Administration Pearls

• Never exceed adult maximum doses regardless of weight: 500 mg on day 1,250 mg daily thereafter for respiratory regimens 1
• Separate from antacids by at least 2 hours: aluminum- or magnesium-containing antacids significantly reduce azithromycin absorption 1
• Oral suspension is preferred for children who cannot swallow tablets; reconstitute with water before administration 1
• Can be given with or without food, though the FDA label notes studies were conducted following a low-fat breakfast 4

Common Pitfalls to Avoid

• Do not use standard 10 mg/kg dosing for strep throat: this results in high recurrence rates; use 12 mg/kg for 5 days instead 1
• Azithromycin is NOT first-line for typical bacterial pneumonia: amoxicillin remains preferred for S. pneumoniae and H. influenzae 1
• Do not use for children <7 years as alternative to macrolides: doxycycline causes dental staining in young children 2
• Monitor for QT prolongation: particularly when co-administered with other QT-prolonging medications 1

Tolerability Profile

• Adverse events occur in approximately 9% of pediatric patients, predominantly mild to moderate gastrointestinal symptoms (abdominal discomfort, diarrhea, nausea, vomiting) 1, 6
• Treatment discontinuation due to adverse effects is rare (0.3%) 3
• Azithromycin has fewer gastrointestinal side effects compared to erythromycin 1
• Higher doses (20-30 mg/kg) are associated with more adverse effects but remain well-tolerated 6