What is the next recommended antibiotic after amoxicillin (amoxicillin) failure in treating streptococcal (strep) throat?

Management of Amoxicillin Treatment Failure in Streptococcal Pharyngitis

After amoxicillin failure in strep throat treatment, clindamycin is the recommended next-line antibiotic due to its high efficacy in eradicating Group A Streptococcus. 1

Treatment Algorithm for Amoxicillin Failure

First-Line Options:

• Clindamycin (oral): 20-30 mg/kg/day in three doses (maximum 300 mg per dose) for 10 days 1
  • Strong recommendation with high-quality evidence
  • Most effective for eradicating persistent strep infection

Alternative Options (in order of preference):

1. Penicillin plus Rifampin combination:

   • Penicillin V: 50 mg/kg/day in four doses for 10 days (maximum 2,000 mg/day)
   • Rifampin: 20 mg/kg/day in one dose for last four days of treatment (maximum 600 mg/day) 1
   • Strong recommendation with high-quality evidence

2. Amoxicillin/clavulanate (Augmentin):

   • 40 mg amoxicillin/kg/day in three doses (maximum 2,000 mg amoxicillin/day) for 10 days 1
   • Strong recommendation with moderate-quality evidence

3. For penicillin-allergic patients:

   • Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 2
   • Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg per dose) for 10 days 1
   • Note: Group A strep resistance to macrolides varies geographically and temporally 1

Clinical Considerations

Reasons for Amoxicillin Failure:

• Poor medication adherence (most common cause)
• Reexposure to infected family members or peers
• Bacterial co-pathogenicity
• Eradication of normal protective pharyngeal flora
• Penicillin/amoxicillin tolerance 3

Important Caveats:

• Complete the full course: Failure to complete the full antibiotic course increases risk of treatment failure and rheumatic fever
• Resistance concerns: Macrolides (azithromycin, clarithromycin) have increasing resistance rates, which vary by geographic region 1
• Monitoring: No routine follow-up throat culture is needed if symptoms resolve 1
• Recurrence management: For multiple recurrences, consider decolonization strategies or tonsillectomy evaluation

Special Populations:

• Children: Adjust dosing based on weight
• Penicillin-allergic patients: Carefully assess the nature of the allergy; immediate hypersensitivity reactions require avoidance of all beta-lactams

Treatment Duration

• Maintain 10-day treatment duration for most antibiotics to prevent rheumatic fever
• Exception: Azithromycin is given for 5 days due to its prolonged tissue half-life 4

Clindamycin's superior efficacy in eradicating persistent strep makes it the preferred choice after amoxicillin failure, with strong supporting evidence for this recommendation. The 10-day duration remains critical for preventing rheumatic fever, regardless of which antibiotic is selected.