What is the recommended dose of azithromycin (macrolide antibiotic) for a 5-year-old male weighing 49 pounds with an upper respiratory tract infection (URTI)?

Azithromycin Dosing for a 5-Year-Old with URTI

Critical First Point: Antibiotics Are Generally NOT Indicated for Uncomplicated URTIs

Most upper respiratory tract infections (URTIs) are viral and do not require antibiotic therapy. 1 The French guidelines explicitly state that URTIs (infections above the vocal cords with normal pulmonary auscultation) are predominantly viral in origin and antibiotics should only be considered in specific circumstances. 1

When Azithromycin IS Appropriate

If this child has specific indications for macrolide therapy (such as suspected atypical pneumonia, pertussis, or documented bacterial infection where beta-lactams are contraindicated), the dosing would be:

Standard Azithromycin Dosing for This Patient

For a 5-year-old weighing 49 pounds (22.2 kg), the recommended dose is 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg (maximum 250 mg) once daily for days 2-5. 2, 3

Specific calculation for this child:

• Day 1: 222 mg (approximately 11 mL of 200 mg/5 mL suspension)
• Days 2-5: 111 mg each day (approximately 2.75 mL of 200 mg/5 mL suspension per day) 3

Using the FDA dosing table for a child weighing 20 kg, the practical dosing would be 5 mL (1 tsp) on day 1, then 2.5 mL (½ tsp) on days 2-5, totaling 15 mL and 600 mg over the treatment course. 3

Important Clinical Context

Age-Appropriate First-Line Therapy

For children over 3 years of age with respiratory infections, the choice between beta-lactams and macrolides depends on the suspected pathogen. 1

• If pneumococcal infection is suspected: Amoxicillin 80-100 mg/kg/day remains first-line therapy 1
• If atypical bacteria (Mycoplasma pneumoniae, Chlamydia pneumoniae) are suspected: Macrolides like azithromycin are reasonable first-line choices 1, 2

When Antibiotics Are Indicated for URTIs

The French guidelines specify antibiotics should only be considered for URTIs when: 1

• High fever (≥38.5°C) persisting for more than 3 days 1
• Associated purulent acute otitis media 1
• Confirmed pneumonia or atelectasis on chest X-ray 1

For children over 3 years with fever persisting >3 days, macrolides are preferred over beta-lactams. 1

Administration Guidelines

• Can be taken with or without food 3
• Total treatment duration: 5 days 2, 3
• Do NOT administer with aluminum- or magnesium-containing antacids as they reduce absorption 2, 4

Common Pitfalls to Avoid

• Avoid underdosing: Ensure the full 10 mg/kg loading dose is given on day 1 2
• Do not use azithromycin as first-line for typical bacterial pneumonia caused by S. pneumoniae or H. influenzae—amoxicillin remains preferred 2
• Monitor for gastrointestinal adverse effects (nausea, vomiting, abdominal pain), which occur in approximately 9% of pediatric patients 4
• Reassess after 48-72 hours: If no improvement, consider alternative diagnosis or pathogen 1

Safety Considerations

• Most common adverse effects are gastrointestinal (mild to moderate severity) 4, 5
• Better tolerated than erythromycin with fewer GI side effects 4, 5
• Safe for use in this age group with established efficacy and safety profile 2, 5