Acute Bacterial Tonsillitis: First-Line Antibiotic Selection
Penicillin V or amoxicillin are the recommended first-line antibiotics for acute bacterial tonsillitis caused by Streptococcus pyogenes, with penicillin V dosed at 250 mg four times daily or 500 mg twice daily for 10 days in adults, and amoxicillin dosed at 500 mg twice daily for 10 days as an equally effective alternative. 1, 2
Why Penicillin V or Amoxicillin Are First-Line
Penicillin V remains the treatment of choice due to proven efficacy, narrow antimicrobial spectrum, excellent safety profile, low cost, and the complete absence of documented penicillin resistance in Group A Streptococcus anywhere in the world. 1, 2, 3
Amoxicillin is an acceptable alternative to penicillin V with comparable efficacy, and is often preferred in younger children because of better palatability and availability as a liquid suspension. 1, 2, 3
Both agents target only Group A Streptococcus without unnecessarily selecting for resistant flora, unlike broader-spectrum alternatives. 1, 2
Critical Treatment Duration
A full 10-day course is mandatory to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever, even if symptoms resolve within 3-4 days. 1, 2, 3
Shortening the course by even a few days results in appreciable increases in treatment failure rates and rheumatic fever risk. 2, 3
The primary goal of antibiotic therapy is not symptomatic improvement but prevention of acute rheumatic fever and suppurative complications, which requires adequate bacterial eradication. 1, 2
Dosing Regimens for Adults
Penicillin V: 250 mg four times daily OR 500 mg twice daily for 10 days 1, 2
Twice-daily dosing of penicillin V is as efficacious as four-times-daily dosing and significantly improves compliance. 1, 4
Dosing Regimens for Children
Amoxicillin: 50 mg/kg once daily (maximum 1000 mg) OR 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1, 2, 3
Penicillin V: 250 mg twice daily or three times daily for children, with dosing adjusted by weight 1, 2
Amoxicillin and penicillin V have identical efficacy against Group A Streptococcus, but amoxicillin is preferred in younger children due to better taste and liquid formulation. 2, 3
Alternative for Poor Compliance
Intramuscular benzathine penicillin G is preferred for patients unlikely to complete a full 10-day oral course, dosed as a single injection of 1.2 million units for patients ≥27 kg or 600,000 units for patients <27 kg. 1, 2, 3
This single-dose option is as effective as oral therapy when adherence cannot be assured, while avoiding the pain and inconvenience of multiple injections. 3
Options for Penicillin-Allergic Patients
Non-Immediate (Delayed) Penicillin Allergy
First-generation cephalosporins are the preferred first-line alternatives with strong, high-quality evidence, as the cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions. 2, 3, 5
Cephalexin: 500 mg twice daily for 10 days (adults) or 20 mg/kg per dose twice daily for 10 days (children, maximum 500 mg per dose) 1, 2, 3
Cefadroxil: 1 g once daily for 10 days (adults) or 30 mg/kg once daily for 10 days (children, maximum 1 g) 1, 2, 3
Immediate/Anaphylactic Penicillin Allergy
All beta-lactam antibiotics must be avoided in patients with immediate hypersensitivity reactions (anaphylaxis, angioedema, respiratory distress, or urticaria within 1 hour) due to up to 10% cross-reactivity risk with cephalosporins. 2, 3, 5
Clindamycin is the preferred choice with only approximately 1% resistance among Group A Streptococcus in the United States and demonstrated high efficacy even in chronic carriers. 2, 3, 5
Azithromycin is an acceptable alternative requiring only 5 days due to its prolonged tissue half-life, but macrolide resistance rates are 5-8% in the United States and vary geographically. 1, 2, 3
Clarithromycin is also an option but carries similar resistance concerns as azithromycin. 1, 2, 3
Common Pitfalls to Avoid
Do not prescribe antibiotics without confirming Group A Streptococcus with either a rapid antigen detection test or throat culture, as clinical features alone cannot reliably distinguish bacterial from viral pharyngitis. 3
Do not use trimethoprim-sulfamethoxazole (Bactrim) for streptococcal pharyngitis, as sulfonamides fail to eradicate Group A Streptococcus in 20-25% of cases. 3, 5
Do not prescribe cephalosporins to patients with immediate/anaphylactic penicillin reactions, as the 10% cross-reactivity risk makes all beta-lactams unsafe in this group. 2, 3, 5
Do not shorten the treatment course below 10 days (except for azithromycin's 5-day regimen), as this dramatically increases treatment failure rates and rheumatic fever risk. 2, 3
Do not prescribe broad-spectrum cephalosporins (cefuroxime, cefdinir, cefpodoxime) when narrow-spectrum first-generation agents are appropriate, as they are more expensive and more likely to select for antibiotic-resistant flora. 2, 5
Adjunctive Symptomatic Treatment
Acetaminophen or NSAIDs (such as ibuprofen) should be considered for moderate to severe symptoms or high fever. 2, 3
Aspirin must be avoided in children due to the risk of Reye syndrome. 2, 3
Corticosteroids are not recommended as adjunctive therapy. 2
Post-Treatment Considerations
Routine follow-up throat cultures are not recommended for asymptomatic patients who have completed therapy. 2, 3
Patients are generally considered non-contagious after 24 hours of antibiotic therapy. 3
Follow-up testing should only be considered in special circumstances, such as patients with a history of rheumatic fever or persistent symptoms. 2, 3