What is the appropriate antibiotic regimen for a patient with a bacterial sore throat?

Treatment of Bacterial Sore Throat

For bacterial sore throat (Group A Streptococcal pharyngitis), amoxicillin 500 mg twice daily for 10 days is an appropriate first-line antibiotic regimen. 1, 2

Diagnosis Assessment

Before initiating antibiotics, confirm bacterial etiology using:

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

  1. Tonsillar exudates
  2. Tender anterior cervical lymph nodes
  3. Lack of cough
  4. Fever

• Patients with 0-2 criteria are unlikely to have GAS infection and generally don't require antibiotics

• Patients with 3-4 criteria should be tested with rapid antigen detection test (RADT) and/or throat culture 2

First-Line Treatment Options

For confirmed or highly suspected bacterial pharyngitis:

1. Amoxicillin:

   • Adults: 500 mg twice daily for 10 days 1, 2
   • Alternative dosing: 50 mg/kg once daily (max 1000 mg) or 25 mg/kg twice daily (max 500 mg per dose) for 10 days 2

2. Penicillin V:

   • Adults: 250 mg 4 times daily or 500 mg twice daily for 10 days 1, 2

3. Benzathine Penicillin G (intramuscular):

   • For patients with anticipated compliance issues
   • Adults ≥27 kg: 1,200,000 U as a single dose 1, 2

Alternative Treatment Options (Penicillin Allergy)

For patients with penicillin allergy:

1. Cephalexin: 20 mg/kg twice daily (max 500 mg per dose) for 10 days 1, 2

   • Avoid in patients with immediate-type hypersensitivity to penicillin

2. Clindamycin: 7 mg/kg three times daily (max 300 mg per dose) for 10 days 1, 2

3. Azithromycin: 12 mg/kg once daily (max 500 mg) for 5 days 1, 2, 3

   • Note: GAS resistance to macrolides is well-known and varies geographically

4. Clarithromycin: 7.5 mg/kg twice daily (max 250 mg per dose) for 10 days 1, 2

   • Note: GAS resistance to macrolides is well-known and varies geographically

Importance of Completing Full Course

• Complete the full 10-day course of antibiotics (except for azithromycin, which is 5 days) to:

  • Prevent acute rheumatic fever
  • Ensure complete eradication of Group A Streptococcus
  • Reduce risk of treatment failure 2

• Even if symptoms improve before completion, patients should be advised to complete the full course 2

Symptomatic Treatment

In addition to antibiotics, recommend:

• NSAIDs or acetaminophen for pain and fever
• Warm salt water gargles
• Throat lozenges 2

Clinical Considerations

• Duration: The 10-day duration for beta-lactams is critical for preventing rheumatic fever and ensuring bacterial eradication 1
• Efficacy: Antibiotics reduce symptoms of sore throat, fever, and headache by about 50%, with maximum effect at around day 3-4 4, 5
• Complications: Antibiotics significantly reduce the risk of suppurative complications like peritonsillar abscess (quinsy) and acute otitis media 4, 5
• Compliance: Once-daily amoxicillin regimens may be as effective as twice-daily regimens and could improve compliance 6

Cautions

• Overuse of antibiotics promotes bacterial resistance and disturbs natural microbial ecology 7
• Penicillin failure rates have increased since the 1970s, sometimes exceeding 20% 7
• Patients with a history of anaphylaxis, angioedema, or respiratory distress should avoid all β-lactams 2

Antibiotics should not be used in patients with likely viral pharyngitis (those with cough, rhinorrhea, hoarseness, oral ulcers) or those with low Centor scores (0-2) 1, 2.