What are the typical doses of commonly used pediatric antibiotics, such as amoxicillin (Amoxil), cephalexin (Keflex), and clindamycin, in community-acquired infections?

Pediatric Antibiotic Dosing in Community-Acquired Infections

Amoxicillin Dosing

For community-acquired respiratory infections in children over 3 months, amoxicillin 90 mg/kg/day divided into 2 doses is the definitive first-line treatment, providing superior coverage against resistant Streptococcus pneumoniae. 1, 2

Standard Dosing by Indication

Respiratory Tract Infections (Pneumonia, Sinusitis):

• Mild to moderate infections: 45 mg/kg/day divided every 12 hours 1
• Severe infections or high pneumococcal resistance areas: 90 mg/kg/day divided every 12 hours (maximum 4 g/day) 1, 2
• Duration: 7-10 days for most respiratory infections; 10 days specifically for pneumonia 1

Group A Streptococcal Infections (Pharyngitis, Scarlet Fever):

• Dosage: 50-75 mg/kg/day divided into 2 doses for 10 days (maximum 1000 mg per dose) 3, 1
• Patients become non-contagious after 24 hours of therapy 1

Infants Under 3 Months:

• Maximum dose: 30 mg/kg/day divided every 12 hours due to immature renal function 4
• Treatment duration minimum 48-72 hours beyond symptom resolution 4

Administration Considerations

• Take at the start of meals to minimize gastrointestinal intolerance 4
• Oral suspension must be shaken well before each use 4
• Reconstituted suspension expires after 14 days; refrigeration preferred but not required 4

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Amoxicillin-Clavulanate (Augmentin) Dosing

For β-lactamase producing organisms or incompletely immunized children, amoxicillin-clavulanate provides essential coverage, with dosing based on the amoxicillin component. 3, 1

Dosing Recommendations

Standard Dose:

• 45 mg/kg/day of amoxicillin component divided into 3 doses 3, 1

High-Dose Regimen (for severe infections or high resistance):

• 90 mg/kg/day of amoxicillin component divided into 2 doses 3, 1, 2
• Maximum daily dose: 4000 mg (4 g) of amoxicillin component 1

Specific Indications:

• β-lactamase producing Haemophilus influenzae: 45 mg/kg/day in 3 doses OR 90 mg/kg/day in 2 doses 3, 1
• Incompletely immunized children with pneumonia: 90 mg/kg/day in 2 doses 1, 2
• Concurrent purulent acute otitis media: 80-90 mg/kg/day 1

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Cephalexin (Keflex) Dosing

Cephalexin provides coverage for methicillin-susceptible Staphylococcus aureus and is dosed at 75-100 mg/kg/day divided into 3-4 doses. 3

Standard Dosing

• Oral dosage: 75-100 mg/kg/day divided into 3 or 4 doses 3
• Maximum consideration: For severe infections, doses up to 100 mg/kg/day may be warranted 3

Important Caveat

• Recent evidence suggests cephalexin may be as effective as clindamycin for uncomplicated skin infections even when MRSA is present, provided adequate drainage is performed 5
• Close follow-up within 48-72 hours is critical regardless of antibiotic choice 5

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Clindamycin Dosing

Clindamycin is the preferred agent for MRSA infections and penicillin-allergic patients, with dosing varying by route and infection severity. 3, 6, 7

Oral Dosing

Standard Infections:

• 30-40 mg/kg/day divided into 3-4 doses 3, 6
• FDA labeling: 8-16 mg/kg/day for serious infections; 16-20 mg/kg/day for severe infections 7

Specific Pathogens:

• MRSA (clindamycin-susceptible): 30-40 mg/kg/day in 3-4 doses 3, 6
• Group A Streptococcus: 40 mg/kg/day in 3 doses 3, 6
• Methicillin-susceptible Staphylococcus aureus: 30-40 mg/kg/day in 3-4 doses 3, 6

Intravenous Dosing

Pneumonia and Serious Infections:

• 10-13 mg/kg/dose every 6-8 hours (maximum 40 mg/kg/day total) 6
• Alternative dosing: 40 mg/kg/day divided every 6-8 hours 3, 6

MRSA Pneumonia (stable patients without bacteremia):

• 10-13 mg/kg/dose IV every 6-8 hours 6

Severe Group A Streptococcal Infections:

• 40 mg/kg/day every 6-8 hours 6

Critical Considerations

• Only use clindamycin when local MRSA resistance rates are <10% 6
• Be aware of inducible resistance in erythromycin-resistant MRSA strains 6
• Take with full glass of water to avoid esophageal irritation 7
• Capsules not suitable for children unable to swallow whole; use oral solution instead 7
• Discontinue immediately if significant diarrhea develops (risk of Clostridioides difficile) 7

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Macrolides (Azithromycin) Dosing

For atypical pathogens (Mycoplasma, Chlamydophila) in children ≥5 years, azithromycin is the preferred agent. 3, 2

Standard Dosing

• Day 1: 10 mg/kg once daily 3, 2
• Days 2-5: 5 mg/kg once daily 3, 2

Combination Therapy

• May be added to amoxicillin for children ≥5 years when atypical pathogens are suspected 2

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Common Pitfalls to Avoid

Underdosing Amoxicillin:

• Using 40-45 mg/kg/day instead of recommended 90 mg/kg/day for pneumonia is a dangerous error that fails to overcome pneumococcal resistance 2

Inappropriate Macrolide Use:

• Macrolides should not be first-line for presumed bacterial pneumonia in children <5 years 2

Failure to Consider MRSA:

• In severe pneumonia with necrotizing infiltrates, empyema, or recent influenza, add vancomycin or clindamycin to beta-lactam therapy 2

Inadequate Follow-Up:

• Reassess all patients at 48-72 hours; lack of improvement requires reevaluation and possible treatment adjustment 1, 2

Ignoring Local Resistance Patterns:

• Clindamycin should only be used when local MRSA clindamycin resistance is <10% 6