Cephalexin Dosing for Acute Bacterial Tonsillopharyngitis in Children
For otherwise healthy children with acute bacterial tonsillopharyngitis (Group A Streptococcus), cephalexin should be dosed at 20 mg/kg per dose twice daily (maximum 500 mg per dose) for a full 10-day course. 1
Dosing Regimen
The Infectious Diseases Society of America (IDSA) strongly recommends cephalexin at 20 mg/kg/dose twice daily (maximum 500 mg/dose) for 10 days as a first-line alternative for children with non-immediate penicillin allergy. 1, 2 This regimen has strong, high-quality evidence supporting its efficacy in eradicating Group A Streptococcus from the pharynx. 1
Key Dosing Parameters:
- Dose: 20 mg/kg per dose 1, 2
- Frequency: Twice daily (every 12 hours) 1, 3
- Maximum single dose: 500 mg 1, 2
- Duration: 10 days (mandatory) 1, 2
When to Use Cephalexin
Cephalexin is appropriate for children with non-immediate (non-anaphylactic) penicillin allergy. 1, 2 The cross-reactivity risk between penicillin and first-generation cephalosporins is only approximately 0.1% in patients with non-severe, delayed penicillin reactions. 2
Critical Contraindication:
Do NOT use cephalexin in children with immediate/anaphylactic penicillin reactions (anaphylaxis, angioedema, respiratory distress, or urticaria within 1 hour of penicillin administration), as up to 10% cross-reactivity exists with all beta-lactam antibiotics. 1, 2 For these patients, clindamycin 7 mg/kg/dose three times daily for 10 days is the preferred alternative. 1, 2
Why This Specific Regimen
The 10-day duration is non-negotiable for preventing acute rheumatic fever and achieving maximal pharyngeal eradication of Group A Streptococcus. 1, 2 Shortening the course by even a few days results in appreciable increases in treatment failure rates and rheumatic fever risk. 2
Twice-daily dosing (rather than three or four times daily) improves adherence while maintaining equivalent bacteriologic and clinical cure rates of approximately 87-90%. 3 Research demonstrates that cephalexin dosed twice daily achieves bacteriologic cure in 87% of children with streptococcal tonsillopharyngitis, comparable to three-times-daily dosing (81%) and once-daily cefadroxil (81%). 3
Alternative First-Generation Cephalosporin
Cefadroxil 30 mg/kg once daily (maximum 1 gram) for 10 days is an equally effective alternative with the advantage of once-daily dosing. 1, 2 This may further improve adherence in families struggling with twice-daily administration. 1
Comparison with Penicillin
First-generation cephalosporins like cephalexin are preferred over penicillin V for penicillin-allergic patients due to strong, high-quality evidence, narrow spectrum activity, proven efficacy, and low cost. 1, 2 While penicillin V remains the drug of choice for non-allergic patients, cephalexin offers superior bacteriologic eradication rates (90%) compared to penicillin V (78-84%) in head-to-head studies. 4, 5
Common Pitfalls to Avoid
Do not prescribe shorter courses than 10 days (except azithromycin's 5-day regimen for immediate penicillin allergy), as this dramatically increases treatment failure and rheumatic fever risk. 1, 2
Do not use cephalexin in patients with immediate hypersensitivity to penicillin (hives, angioedema, bronchospasm within 1 hour) due to 10% cross-reactivity risk. 1, 2
Do not prescribe broad-spectrum cephalosporins (cefdinir, cefixime, cefpodoxime) when narrow-spectrum first-generation agents like cephalexin are appropriate, as they are more expensive and more likely to select for antibiotic-resistant flora. 2
Do not underdose—ensure the full 20 mg/kg per dose is prescribed, not lower doses that may be inadequate for resistant strains. 1
Age-Specific Considerations
Younger children (ages 1-5 years) have significantly higher rates of recurrent infections and treatment failure compared to older children (ages 6-17 years), regardless of antibiotic choice. 4 This does not change the dosing regimen but should prompt closer follow-up in younger patients. 4
Clinical Monitoring
Children should demonstrate clinical improvement within 48-72 hours of starting therapy. 2 If no improvement occurs within this timeframe, consider:
- Non-compliance with medication
- Chronic carrier state with concurrent viral infection
- Alternative diagnosis
- Need for different antibiotic class (clindamycin or macrolide if not already used) 2
Routine post-treatment throat cultures are NOT recommended for asymptomatic patients who have completed therapy. 2 Testing should only be considered in special circumstances such as patients with a history of rheumatic fever. 2
Adjunctive Symptomatic Treatment
Acetaminophen or NSAIDs (such as ibuprofen) should be offered for moderate to severe symptoms or high fever. 2 Aspirin must be avoided in children due to Reye syndrome risk. 2 Corticosteroids are not recommended as adjunctive therapy. 2