Treatment of Group A Streptococcal (GAS) Infection in Adults
For adults with confirmed GAS pharyngitis, prescribe penicillin V 250 mg three to four times daily OR 500 mg twice daily for 10 days, or alternatively amoxicillin 50 mg/kg once daily (maximum 1,000 mg) for 10 days. 1, 2
First-Line Antibiotic Therapy
Penicillin remains the treatment of choice based on its narrow spectrum, proven efficacy in preventing acute rheumatic fever, safety profile, and low cost. 1, 3 The specific dosing for adults is:
- Oral penicillin V: 250 mg three to four times daily OR 500 mg twice daily for 10 days 1
- Amoxicillin: 50 mg/kg once daily (maximum 1,000 mg) for 10 days, which may enhance adherence due to once-daily dosing 2
- Intramuscular benzathine penicillin G: 1.2 million units as a single dose if oral adherence is a concern 1, 2
The 10-day duration is critical—it maximizes bacterial eradication from the pharynx and prevents acute rheumatic fever, which remains the primary justification for antibiotic treatment. 2, 3
Treatment for Penicillin-Allergic Patients
For patients with non-anaphylactic penicillin allergy:
- First-generation cephalosporins (e.g., cephalexin) for 10 days 1, 2
- These should NOT be used in patients with immediate hypersensitivity to β-lactam antibiotics 1
For patients with anaphylactic penicillin allergy:
- Erythromycin estolate or ethyl succinate: 20-40 mg/kg/day (maximum 1 g/day) divided two to three times daily for 10 days 1
- Azithromycin: 5-day course (the only antibiotic approved for shorter duration) 2
- Clindamycin or clarithromycin: 10 days of treatment 2
Diagnostic Confirmation Required
Do not treat without confirming the diagnosis through testing. 3 Clinical features alone cannot reliably distinguish bacterial from viral pharyngitis. 3
- Use rapid antigen detection test (RADT) or throat culture before initiating antibiotics 2, 3
- A positive RADT is diagnostic and does not require backup culture 2
- Adults do not require backup cultures after negative RADT, given the exceptionally low risk of acute rheumatic fever 3
Adjunctive Symptomatic Management
- Acetaminophen or NSAIDs for moderate to severe symptoms or high fever 2, 3
- Avoid aspirin in younger patients due to risk of Reye syndrome 2, 4
- Warm salt water gargles may provide temporary relief 4
Critical Pitfalls to Avoid
Do not prescribe shorter courses of penicillin or amoxicillin (less than 10 days) as this is not supported by current guidelines and may increase risk of treatment failure and inadequate prevention of rheumatic fever. 2 While some research suggests 6-7 day courses may have comparable efficacy 5, 6, major guidelines do not endorse this approach because the 10-day duration has proven efficacy in preventing acute rheumatic fever. 2, 7
Do not prescribe broad-spectrum antibiotics unnecessarily when narrow-spectrum options like penicillin are effective. 2
Do not treat asymptomatic household contacts unless there is a documented outbreak requiring intervention. 1, 3
Follow-Up Considerations
- Routine post-treatment throat cultures are not recommended unless symptoms persist or recur 2, 3
- Patients with recurrent episodes should be evaluated to determine whether they are experiencing true recurrent infections or are chronic carriers with concurrent viral infections 2
- For treatment failures after penicillin, consider clindamycin as an alternative 8