What is the recommended dose of amoxicillin (Amoxicillin) for a 6-year-old patient with community-acquired pneumonia (CAP) weighing 66 pounds and being treated as an outpatient?

Amoxicillin Dosing for Pediatric Community-Acquired Pneumonia

Recommended Dose

For a 6-year-old patient weighing 66 lbs (30 kg) with outpatient CAP, prescribe amoxicillin 90 mg/kg/day divided into 2 or 3 doses, which equals 2700 mg/day total (900 mg three times daily or 1350 mg twice daily) for 5 days. 1, 2

Dosing Algorithm

Step 1: Calculate the High-Dose Regimen

• Use 90 mg/kg/day as the standard dose for CAP in children, which provides optimal coverage against β-lactamase-producing Haemophilus influenzae and penicillin-resistant Streptococcus pneumoniae 1
• For this 30 kg patient: 90 mg/kg/day × 30 kg = 2700 mg/day total 1

Step 2: Choose Dosing Frequency

• Three times daily dosing (900 mg TID) is the traditional approach and maintains more consistent drug levels above the MIC 2
• Twice daily dosing (1350 mg BID) is an acceptable alternative that improves compliance while maintaining adequate pharmacokinetic parameters 3, 4, 2
• The twice-daily regimen has demonstrated non-inferiority to three-times-daily dosing in recent trials, though some evidence suggests slightly longer time to cough resolution 4

Step 3: Determine Treatment Duration

• 5 days of therapy is the recommended duration for uncomplicated CAP in outpatient settings 4, 5, 2
• A 5-day course demonstrated non-inferiority to 10-day treatment with similar clinical outcomes, adverse events, and antimicrobial resistance patterns 4, 5
• Three-day courses showed unacceptably high failure rates (40%) and should be avoided 5

Critical Dosing Considerations

Maximum Dose Limits

• The absolute maximum is 4000 mg/day of amoxicillin, regardless of weight 1
• This patient's calculated dose of 2700 mg/day is well below this ceiling 1

Immunization Status Matters

• If the child has incomplete immunization against H. influenzae type b or S. pneumoniae, consider switching to amoxicillin-clavulanate instead of amoxicillin monotherapy 2
• For fully immunized children, amoxicillin monotherapy remains first-line 2

When to Add or Switch Antibiotics

• If symptoms persist after 48-72 hours with good clinical condition in a child >5 years old, consider adding a macrolide to cover atypical pathogens 2
• Schedule clinical reassessment at approximately 72 hours after starting treatment to evaluate symptom resolution 2

Common Pitfalls to Avoid

• Do not use lower doses (45 mg/kg/day or the older WHO recommendation of 15 mg/kg/dose TID): These provide inadequate coverage for resistant pathogens commonly encountered in CAP 1, 3
• Do not extend to 10 days routinely: Longer courses increase adverse events without improving outcomes in uncomplicated cases 4, 5
• Do not use 3-day courses: These are associated with treatment failure rates up to 40% 5

Practical Administration

• High-dose amoxicillin (90 mg/kg/day) has been associated with higher incidence of gastritis and diarrhea compared to other antibiotics, so counsel families accordingly 1
• Twice-daily dosing may improve adherence, particularly important for working families 3, 4
• Ensure follow-up contact within 72 hours to assess clinical response 2