Is cephalexin (a cephalosporin antibiotic) an effective treatment for streptococcal pharyngitis?

Cephalexin for Streptococcal Pharyngitis

Cephalexin is an effective alternative treatment for streptococcal pharyngitis, but penicillin V or amoxicillin remains the first-line treatment according to current guidelines. 1

Diagnosis of Streptococcal Pharyngitis

Before considering antibiotic treatment, proper diagnosis is essential:

• Use Centor criteria to assess likelihood of Group A Streptococcal (GAS) infection:

  • Fever by history
  • Tonsillar exudates
  • Tender anterior cervical adenopathy
  • Absence of cough 1

• Clinical features suggesting viral etiology (not strep throat):

  • Cough
  • Rhinorrhea (runny nose)
  • Hoarseness
  • Oral ulcers 1

• Testing recommendations:

  • 0-2 Centor criteria: No testing needed (unlikely GAS)
  • 3-4 Centor criteria: Test with rapid antigen detection test (RADT) and/or throat culture 1

Treatment Recommendations

First-Line Treatment

• Penicillin V or amoxicillin for 10 days is the recommended first-line treatment for confirmed strep throat 1
• Amoxicillin dosing: 50 mg/kg once daily (maximum 1000 mg) for 10 days 1

Role of Cephalexin

• Cephalexin is indicated for respiratory tract infections caused by Streptococcus pyogenes 2
• Dosing: 20 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1
• FDA notes: "Penicillin is the usual drug of choice in the treatment and prevention of streptococcal infections, including the prophylaxis of rheumatic fever" 2
• While cephalexin is effective for eradicating streptococci, the FDA notes that "substantial data establishing the efficacy of cephalexin in the subsequent prevention of rheumatic fever are not available" 2

For Penicillin-Allergic Patients

• Cephalexin is an appropriate choice for non-anaphylactic penicillin allergy 1
• Other alternatives: clindamycin, clarithromycin, or azithromycin 1

Efficacy Considerations

• Cephalexin has demonstrated efficacy in treating streptococcal pharyngitis with cure rates of over 90% 3, 4
• Some research suggests that oral cephalosporins may have lower failure rates compared to penicillin (11% vs 23%) 5
• However, current guidelines from the Infectious Diseases Society of America (IDSA) still recommend penicillin as first-line therapy 6

Important Clinical Considerations

• A full 10-day course of antibiotics is critical to prevent rheumatic fever 1
• Twice-daily dosing of cephalexin is as effective as four-times-daily dosing, which may improve adherence 3
• Patients are considered non-contagious after 24 hours of appropriate antibiotic therapy 1
• Common side effects of cephalexin include gastrointestinal upset, rash, and urticaria, but these are relatively infrequent 4

Pitfalls to Avoid

• Do not prescribe antibiotics empirically without testing in patients with low probability of strep throat (0-2 Centor criteria) 1
• Do not use cephalexin for presumed viral respiratory infections 1
• Avoid incomplete antibiotic courses, as this increases risk of treatment failure and rheumatic fever 1
• Remember that cephalexin may be less effective against H. influenzae (relevant for otitis media, not strep throat) 4

Summary Algorithm

1. Assess using Centor criteria
2. Test patients with 3-4 Centor criteria using RADT and/or throat culture
3. If positive for GAS:
   • First-line: Penicillin V or amoxicillin for 10 days
   • For non-anaphylactic penicillin allergy: Cephalexin 20 mg/kg twice daily (max 500 mg per dose) for 10 days
   • For anaphylactic penicillin allergy: Clindamycin, clarithromycin, or azithromycin