Pediatric Cephalexin Dosing for Streptococcal Infections
Recommended Dosing Regimen
For children with confirmed or presumed Group A streptococcal pharyngitis or skin infection who cannot receive penicillin or amoxicillin, prescribe cephalexin 20 mg/kg per dose twice daily (maximum 500 mg per dose) for a full 10 days. 1, 2
Weight-Based Dosing Examples
- 10 kg (22 lb): 1–2 teaspoons of 125 mg/5 mL suspension twice daily 2
- 20 kg (44 lb): 2–4 teaspoons of 125 mg/5 mL suspension twice daily (or 1–2 teaspoons of 250 mg/5 mL) 2
- 40 kg (88 lb): 4–8 teaspoons of 125 mg/5 mL suspension twice daily (or 2–4 teaspoons of 250 mg/5 mL) 2
The FDA label specifies that for streptococcal pharyngitis and skin infections in pediatric patients over 1 year of age, the total daily dose may be divided and administered every 12 hours. 2
Critical Treatment Duration
A complete 10-day course is mandatory to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever. 1, 3 Shortening the course by even a few days results in appreciable increases in treatment failure rates and rheumatic fever risk. 1, 4 This requirement applies even when symptoms resolve within 3–4 days. 1
When Cephalexin Is Appropriate
Type of Penicillin Allergy Matters
- Non-immediate (delayed) reactions: Cephalexin is safe and preferred, with only 0.1% cross-reactivity risk in patients with mild, delayed penicillin reactions such as a rash. 1, 3
- Immediate/anaphylactic reactions: Avoid all cephalosporins due to up to 10% cross-reactivity risk with beta-lactams. 1, 3 These reactions include anaphylaxis, angioedema, respiratory distress, or urticaria occurring within 1 hour of penicillin administration. 1
Evidence Supporting Cephalexin
First-generation cephalosporins like cephalexin have strong, high-quality evidence supporting their efficacy as preferred alternatives for penicillin-allergic patients without immediate hypersensitivity. 1, 3 Cephalexin has demonstrated cure rates of 90% or higher in streptococcal infections over 12 years of clinical experience. 5 Studies show cephalexin twice-daily and four-times-daily regimens are equally effective, with failure rates of 7.3% and 5.3% respectively. 6
Alternatives for Immediate Penicillin Allergy
If the child has had anaphylaxis, angioedema, or immediate urticaria to penicillin:
- Clindamycin: 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days—preferred choice with only ~1% resistance in the United States. 1, 3
- Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days—acceptable alternative but 5–8% macrolide resistance exists. 1, 3
- Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg per dose) for 10 days—similar resistance concerns as azithromycin. 1
Common Pitfalls to Avoid
Do not prescribe cephalexin if the child had anaphylaxis, angioedema, or immediate urticaria to amoxicillin or penicillin—the 10% cross-reactivity risk makes this potentially life-threatening. 1, 3
Do not shorten the course below 10 days—even if symptoms improve rapidly, incomplete treatment dramatically increases treatment failure and acute rheumatic fever risk. 1, 4
Do not use trimethoprim-sulfamethoxazole (Bactrim)—sulfonamides fail to eradicate Group A Streptococcus in 20–25% of cases and should never be used for streptococcal pharyngitis. 1
Do not prescribe broad-spectrum cephalosporins (cefdinir, cefuroxime, cefpodoxime) when narrow-spectrum cephalexin is appropriate—they are more expensive and promote antibiotic-resistant flora. 1
Adjunctive Symptomatic Care
- Ibuprofen or acetaminophen for moderate to severe symptoms or high fever (NSAIDs are more effective than acetaminophen). 3
- Avoid aspirin in children due to Reye syndrome risk. 1, 3
- Do not use corticosteroids as adjunctive therapy. 1
Post-Treatment Considerations
Do not order routine follow-up throat cultures for asymptomatic patients who have completed therapy—testing should only be considered in special circumstances such as a history of rheumatic fever. 1, 3