What is the recommended dosage of azithromycin (Zithromax) for a 33-pound toddler with community-acquired pneumonia, otitis media, or sinusitis?

Azithromycin Dosing for a 33-Pound Toddler

For a 33-pound (15 kg) toddler with community-acquired pneumonia, otitis media, or sinusitis, administer azithromycin 10 mg/kg (150 mg) on day 1, followed by 5 mg/kg (75 mg) once daily on days 2 through 5. 1, 2

Weight-Based Dosing Calculation

• A 33-pound toddler weighs approximately 15 kg 2
• The standard 5-day regimen requires:
  • Day 1: 150 mg (10 mg/kg × 15 kg) 1, 2
  • Days 2-5: 75 mg once daily (5 mg/kg × 15 kg) 1, 2
• Using the 200 mg/5 mL suspension formulation, this translates to:
  • Day 1: 3.75 mL
  • Days 2-5: 1.875 mL daily 2

Alternative Dosing Regimens by Indication

For Acute Otitis Media Only

• A 3-day regimen of 10 mg/kg (150 mg) once daily for 3 days is an acceptable alternative 2
• A single 30 mg/kg dose (450 mg) is also FDA-approved for otitis media, though this higher dose is associated with more gastrointestinal adverse effects 2, 3

For Acute Bacterial Sinusitis Only

• A 3-day regimen of 10 mg/kg (150 mg) once daily for 3 days is recommended 2

For Community-Acquired Pneumonia

• The 5-day regimen (10 mg/kg day 1, then 5 mg/kg days 2-5) is the only established effective regimen for pneumonia in this age group 1, 2

Critical Clinical Context

Azithromycin should NOT be used as monotherapy for presumed bacterial pneumonia in children under 5 years. 1

• Amoxicillin 90 mg/kg/day in 2 divided doses remains first-line therapy for bacterial pneumonia in preschool-aged children because it provides superior coverage against Streptococcus pneumoniae, the most common bacterial pathogen 1, 4
• Azithromycin is appropriate as monotherapy only when atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae) are strongly suspected, which is uncommon in children under 5 years 1
• For children ≥5 years with pneumonia where bacterial versus atypical etiology cannot be distinguished clinically, add azithromycin to amoxicillin rather than using it alone 1

Administration and Tolerability

• Azithromycin suspension can be taken with or without food 2
• The medication is generally well-tolerated, with treatment-related adverse events occurring in approximately 9% of pediatric patients 3
• Gastrointestinal complaints (nausea, vomiting, diarrhea, abdominal pain) are the most common side effects and are typically mild to moderate 5, 3
• Children find the taste and color of the oral suspension agreeable, which optimizes compliance 3

Common Pitfalls to Avoid

• Do not use azithromycin monotherapy for empiric treatment of pneumonia in children under 5 years unless atypical pneumonia is strongly suspected based on clinical presentation, as it provides inadequate coverage for pneumococcal disease 1, 4
• Do not confuse the different dosing regimens—the 5-day regimen is required for pneumonia, while 3-day or single-dose regimens are only validated for otitis media and sinusitis 2
• If the child vomits within 30 minutes of receiving a single 30 mg/kg dose for otitis media, re-dosing at the same total dose is appropriate, though safety data for this practice are limited 2

Follow-Up Requirements

• Clinical improvement should be evident within 48-72 hours of starting appropriate antibiotic therapy 4
• If no improvement occurs within this timeframe, re-evaluation is mandatory to assess for treatment failure, complications, or alternative diagnoses 1, 4
• Instruct caregivers to return immediately for worsening respiratory distress, inability to feed or drink, lethargy, persistent high fever, or cyanosis 4