Pharmacotherapy of Group A Streptococcal (GAS) Infections
Penicillin V or amoxicillin for 10 days is the first-line treatment for Group A Streptococcal infections, with amoxicillin preferred in children due to better taste and ease of administration. 1
First-Line Treatment Options
Oral Therapy
Penicillin V oral:
- Children: 250 mg 2-3 times daily for 10 days
- Adolescents/Adults: 500 mg 2 times daily for 10 days 1
Amoxicillin oral (preferred in children):
- 50 mg/kg once daily (maximum 1000 mg) OR
- 25 mg/kg twice daily (maximum 500 mg per dose)
- Duration: 10 days 1
For Penicillin Allergies
Non-anaphylactic penicillin allergy:
- First-generation cephalosporins for 10 days 1
Anaphylactic penicillin allergy:
- Clindamycin: 300-450 mg orally three times daily for 10 days
- Azithromycin: 12 mg/kg once daily (max 500 mg) for 5 days
- Clarithromycin: 10 days 1
Important note: Significant resistance to azithromycin and clarithromycin exists in some parts of the United States 1. While azithromycin offers a shorter treatment course, it has shown lower bacteriologic eradication rates compared to penicillin (38% vs 81%) despite similar clinical success rates 2.
Diagnosis Before Treatment
Treatment should be guided by proper diagnosis using:
- Centor Criteria (tonsillar exudates, tender anterior cervical lymph nodes, lack of cough, fever)
- 0-2 criteria: GAS unlikely, no testing or antibiotics needed
- 3-4 criteria: Test with rapid antigen detection test (RADT) and/or throat culture 1
Treatment Duration and Adherence
- Complete the full 10-day course of antibiotics even if symptoms improve earlier to prevent acute rheumatic fever 1
- The FDA has approved 5-day regimens for certain antibiotics:
Prevention of Complications
Appropriate antibiotic treatment helps prevent:
- Acute rheumatic fever
- Suppurative complications (peritonsillar abscess, cervical lymphadenitis)
- Transmission to close contacts 1
Adjunctive Therapy
- Acetaminophen or NSAIDs for pain and fever relief
- Avoid aspirin in children due to risk of Reye's syndrome 1
- Supportive measures:
- Cold liquids or ice chips
- Gargling with cold water
- Avoiding hot liquids and spicy/hard foods that may irritate the throat 1
Return to School/Work
- Patients should complete at least 24 hours of antibiotics before returning to school or work to reduce transmission risk 1
Special Considerations
- For patients with a history of rheumatic fever, continuous antimicrobial prophylaxis is recommended to prevent recurrences 1
- While once-daily amoxicillin has shown non-inferiority to twice-daily dosing in some studies 5, the standard recommendation remains twice-daily dosing for the full 10-day course
The 10-day treatment duration is crucial for GAS pharyngitis to ensure complete eradication and prevent serious complications, particularly acute rheumatic fever, even though shorter courses may show similar clinical efficacy in some studies 5, 6.