Recommended Antibiotic for Strep A Infections
Penicillin or amoxicillin remains the first-line treatment for Group A Streptococcus infections in patients without penicillin allergy, with a full 10-day course required to prevent acute rheumatic fever. 1, 2
First-Line Treatment for Non-Allergic Patients
Penicillin V or amoxicillin should be prescribed for all patients without penicillin allergy due to proven efficacy, narrow spectrum, safety, low cost, and zero documented resistance worldwide. 1, 2
Specific Dosing Regimens:
Penicillin V oral: Children receive 250 mg two or three times daily; adolescents and adults receive 250 mg four times daily or 500 mg twice daily for 10 days (strong, high-quality evidence). 1
Amoxicillin oral: 50 mg/kg once daily (maximum 1,000 mg) or alternatively 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days (strong, high-quality evidence). 1
Penicillin G benzathine intramuscular: Single dose of 600,000 units for patients <60 lbs (27 kg) or 1,200,000 units for patients ≥60 lbs (strong, high-quality evidence). 1
The twice-daily dosing of penicillin is as effective as more frequent dosing and improves compliance, while once-daily penicillin shows 12 percentage points lower cure rates and should be avoided. 3
Treatment for Penicillin-Allergic Patients
Non-Immediate (Non-Anaphylactic) Penicillin Allergy:
First-generation cephalosporins are the preferred alternatives with only 0.1% cross-reactivity risk in patients with delayed, non-severe reactions. 2, 4
Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg per dose) for 10 days in children; 500 mg twice daily for adults (strong, high-quality evidence). 1, 2
Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days (strong, high-quality evidence). 1, 4
Immediate/Anaphylactic Penicillin Allergy:
All beta-lactam antibiotics must be avoided due to up to 10% cross-reactivity risk with cephalosporins in patients with immediate hypersensitivity reactions (anaphylaxis, angioedema, respiratory distress, or urticaria within 1 hour). 1, 2
Clindamycin is the preferred choice with approximately 1% resistance rate among Group A Streptococcus in the United States and demonstrated high efficacy even in chronic carriers. 2, 4
- Clindamycin: 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days in children; 300 mg three times daily for adults (strong, moderate-quality evidence). 1, 2
Macrolides are acceptable alternatives but less preferred due to 5-8% resistance rates in the United States that vary geographically and temporally. 2, 4
Azithromycin: 12 mg/kg once daily (maximum 500 mg) for only 5 days due to prolonged tissue half-life (strong, moderate-quality evidence). 1, 2, 5
Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg per dose) for 10 days (strong, moderate-quality evidence). 1, 4
Critical Treatment Duration Requirements
A full 10-day course is essential for all antibiotics except azithromycin to achieve maximal pharyngeal eradication and prevent acute rheumatic fever, with shortened courses dramatically increasing treatment failure rates and rheumatic fever risk. 1, 2, 4
Azithromycin is the only exception requiring just 5 days due to its unique pharmacokinetics and prolonged tissue half-life. 2, 4, 5
Special Clinical Situations
Necrotizing Fasciitis and Streptococcal Toxic Shock Syndrome:
Clindamycin plus penicillin is the recommended combination (A-II evidence) for severe invasive Group A Streptococcus infections, as clindamycin suppresses toxin production and modulates cytokine (TNF) production beyond its antimicrobial activity. 1, 2
- Penicillin: 2-4 million units every 4-6 hours IV plus Clindamycin: 600-900 mg every 8 hours IV. 1
Chronic Carriers:
Chronic carriers generally do not require treatment as they are unlikely to spread infection or develop complications. 1, 2
When treatment is indicated for chronic carriers, clindamycin 20-30 mg/kg per day in three doses (maximum 300 mg per dose) for 10 days is particularly effective due to superior eradication rates. 1, 2, 4
Common Pitfalls to Avoid
Do not prescribe once-daily penicillin as it shows significantly lower cure rates compared to twice-daily or more frequent dosing. 3
Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions due to the 10% cross-reactivity risk. 1, 2
Do not shorten antibiotic courses below 10 days (except azithromycin's 5-day regimen) as this dramatically increases treatment failure and rheumatic fever risk. 2, 4
Do not use trimethoprim-sulfamethoxazole (Bactrim) for strep throat as it has high resistance rates and is not effective against Group A Streptococcus. 2
Do not assume all penicillin-allergic patients cannot receive cephalosporins - only those with immediate/anaphylactic reactions should avoid them. 2
Do not prescribe macrolides as first-line therapy when penicillin can be used, as this unnecessarily increases selection pressure for antibiotic resistance. 2, 5
Be aware of local macrolide resistance patterns before prescribing azithromycin or clarithromycin, as resistance varies significantly by geography. 2, 4, 5
Post-Treatment Follow-Up
Routine post-treatment throat cultures are not recommended for asymptomatic patients who have completed therapy. 2, 4
Follow-up testing should only be considered in special circumstances such as patients with a history of rheumatic fever, during community outbreaks, or when excessive anxiety exists about Group A Streptococcal infections. 1, 4