What are the recommended antibiotics (Abx) for streptococcal pharyngitis?

Recommended Antibiotics for Streptococcal Pharyngitis

Penicillin V is the first-line antibiotic treatment for streptococcal pharyngitis, administered for a full 10-day course to prevent acute rheumatic fever. 1

First-Line Treatment Options

• Penicillin V:

  • Adults: 250 mg three times daily for 10 days
  • Children: 600,000 U for <27 kg and 1,200,000 U for ≥27 kg for 10 days 1

• Amoxicillin:

  • 50 mg/kg once daily (maximum 1000 mg) or
  • 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1
  • Note: Twice-daily dosing of penicillin/amoxicillin is as effective as more frequent dosing, improving compliance 2

Alternative Options for Penicillin-Allergic Patients

1. Clindamycin (preferred alternative):

   • 300-450 mg orally three times daily for 10 days
   • Excellent coverage with 99.5% susceptibility against Group A Streptococcus 1

2. Macrolides (second option):

   • Azithromycin: 12 mg/kg once daily (max 500 mg) for 5 days
   • Note: Macrolide resistance has increased from 4-5% to 8-9% in recent years 1
   • Caution: 10-day clarithromycin regimens show better eradication rates than 5-day azithromycin regimens (91% vs 82%) 3

Special Considerations

Severe Infections

• Combination therapy with rifampin plus clindamycin is recommended 1
• For hospitalized children:
  • Clindamycin: 10-13 mg/kg/dose IV every 6-8 hours
  • Vancomycin: 40-60 mg/kg/day divided every 6-8 hours IV (first choice for severe infections) 1

Treatment Duration

• A full 10-day course is essential for all streptococcal infections to prevent acute rheumatic fever 1
• Short-course therapy (≤5 days) with penicillin is less effective for clinical cure and bacterial eradication compared to standard 10-day regimens 4

Treatment Failures

• Penicillin failure rates have increased from 2-10% in the 1970s to approximately 30% currently 5
• Common causes of treatment failure:
  • Poor compliance with 10-day regimen
  • Reexposure to infected contacts
  • Copathogenicity with protective bacterial strains
  • Penicillin tolerance 5

Monitoring and Follow-up

• Expect clinical improvement within 48-72 hours of starting appropriate therapy 1
• Follow-up throat cultures are not routinely indicated for asymptomatic patients who have completed appropriate therapy 1
• If symptoms persist or worsen despite appropriate therapy, consider:
  • Evaluation for suppurative complications (e.g., peritonsillar abscess)
  • Alternative antibiotic therapy
  • Possible imaging or referral 1

Common Pitfalls to Avoid

1. Inadequate treatment duration: Shortened courses increase risk of treatment failure and complications
2. Once-daily penicillin dosing: Associated with 12% lower cure rates than more frequent dosing 2
3. Overuse of broad-spectrum antibiotics: Macrolides and cephalosporins are on the "Highest Priority Critically Important Antimicrobials" list and should be reserved for penicillin-allergic patients 4
4. Failure to consider compliance: Twice-daily dosing improves adherence while maintaining efficacy 2
5. Neglecting to complete the full course: Even with symptom improvement, the full 10-day course is necessary to prevent rheumatic fever 1