What is the appropriate antibiotic choice and dosing for an otherwise healthy 4-year-old child weighing 15.6 kg?

Antibiotic Choice and Dosing for a 4-Year-Old Child Weighing 15.6 kg

For a 4-year-old child weighing 15.6 kg requiring antibiotic therapy, amoxicillin is the first-line choice for most common pediatric infections at a dose of 45 mg/kg/day divided every 12 hours (approximately 350 mg twice daily or 3.5 mL of 250 mg/5 mL suspension twice daily) for mild-to-moderate respiratory tract infections, or 90 mg/kg/day divided every 12 hours (approximately 700 mg twice daily or 7 mL of 250 mg/5 mL suspension twice daily) for severe infections or areas with high pneumococcal resistance. 1, 2

Indication-Specific Dosing Algorithm

For Community-Acquired Pneumonia or Lower Respiratory Tract Infections

• Mild-to-moderate cases without risk factors: Amoxicillin 45 mg/kg/day divided every 12 hours = 351 mg per dose (approximately 350 mg twice daily) 1, 2
• Severe infections or high-resistance risk factors: Amoxicillin 90 mg/kg/day divided every 12 hours = 702 mg per dose (approximately 700 mg twice daily) 1, 2
• Risk factors requiring high-dose therapy include: age <2 years, daycare attendance, antibiotic use within past 30 days, or areas with >10% penicillin-resistant S. pneumoniae 1

For Group A Streptococcal Pharyngitis (Strep Throat)

• Recommended dose: 50-75 mg/kg/day divided into 2 doses for 10 days = 390-585 mg twice daily (not exceeding 1000 mg per dose) 1
• Treatment duration must be 10 full days to prevent acute rheumatic fever 2

For Acute Otitis Media (Ear Infection)

• Standard dose: 45 mg/kg/day divided every 12 hours for uncomplicated cases 1
• High-dose amoxicillin-clavulanate (Augmentin): 90 mg/kg/day of amoxicillin component if antibiotic use within past 4-6 weeks or β-lactamase-producing organisms suspected 1

For Skin and Soft Tissue Infections

• Mild-to-moderate: 25 mg/kg/day divided every 12 hours = 195 mg twice daily 2
• Severe: 45 mg/kg/day divided every 12 hours = 351 mg twice daily 2

When to Use Amoxicillin-Clavulanate (Augmentin) Instead

Switch to amoxicillin-clavulanate at 90 mg/kg/day of the amoxicillin component when:

• β-lactamase-producing organisms (H. influenzae, M. catarrhalis) are suspected 1
• Recent antibiotic exposure within 30 days 1
• Incomplete H. influenzae type b vaccination 1
• Concurrent purulent acute otitis media with pneumonia 1
• Treatment failure after 48-72 hours on standard amoxicillin 1

Alternative Antibiotics for Penicillin Allergy

For Non-Anaphylactic Penicillin Allergy

• Cefdinir or cefuroxime (second- or third-generation cephalosporins) at standard pediatric dosing 1

For Type I Hypersensitivity (Anaphylactic) Reactions

• Clindamycin: 40 mg/kg/day divided every 6-8 hours (oral: 30-40 mg/kg/day in 3-4 doses) for Group A Streptococcus or MRSA coverage 3
• For this 15.6 kg child: approximately 156 mg every 6 hours or 208 mg every 8 hours 3

Critical Treatment Monitoring

• Clinical improvement should occur within 48-72 hours of starting appropriate antibiotic therapy 1
• If no improvement by 48-72 hours: reevaluate for atypical pathogens (consider adding macrolide), treatment failure, or complications requiring hospitalization 1
• Fever typically resolves within 24-48 hours for pneumococcal infections, though cough may persist longer 1
• Complete the full prescribed course (typically 7-10 days for respiratory infections, 10 days for pneumonia, 10 days mandatory for strep throat) even if symptoms improve 1, 2

Administration Considerations

• Take amoxicillin at the start of meals to minimize gastrointestinal intolerance 2
• Oral suspension preparation: Shake well before each use; can be mixed with formula, milk, fruit juice, or water and administered immediately 2
• Storage: Refrigeration preferred but not required; discard unused suspension after 14 days 2

Common Pitfalls to Avoid

• Do not use the 875 mg tablet formulation in children weighing <40 kg 2
• Do not underdose: The traditional APLS formula (Weight = 2[age+4]) significantly underestimates children's weights by 33.4% on average, which can lead to under-resuscitation 4
• Do not stop antibiotics early when symptoms improve, particularly for strep throat where 10 days is mandatory to prevent rheumatic fever 2
• Do not use amoxicillin alone if β-lactamase-producing organisms are suspected; switch to amoxicillin-clavulanate 1