What are the recommended antibiotics for bacterial pharyngitis?

Recommended Antibiotics for Bacterial Pharyngitis

Penicillin V (250 mg four times daily or 500 mg twice daily) or amoxicillin (50 mg/kg once daily, maximum 1000 mg) for 10 days are the first-line antibiotics for Group A streptococcal pharyngitis due to their proven efficacy, narrow spectrum, safety, and low cost, with no documented penicillin resistance anywhere in the world. 1, 2

First-Line Treatment for Non-Allergic Patients

Penicillin Options

• Penicillin V oral: 250 mg four times daily OR 500 mg twice daily for 10 days in adolescents/adults 1
• Penicillin V oral (children): 250 mg twice or three times daily for 10 days 1
• Amoxicillin oral: 50 mg/kg once daily (maximum 1000 mg) for 10 days—often preferred in children due to better palatability and once-daily dosing 1, 3
• Benzathine penicillin G intramuscular: Single dose of 600,000 units if <27 kg or 1,200,000 units if ≥27 kg—ensures compliance when adherence to oral therapy is uncertain 1, 3

Critical Evidence

• Penicillin V 500 mg twice daily is as effective as four-times-daily dosing and superior to once-daily dosing, which has a 22% bacteriologic failure rate compared to 8% with divided doses 4, 5
• Once-daily penicillin regimens should be avoided due to significantly higher treatment failure rates 5

Treatment Algorithm for Penicillin-Allergic Patients

Step 1: Determine Type of Allergy

Non-immediate (non-anaphylactic) penicillin allergy:

• First-generation cephalosporins are preferred with strong, high-quality evidence 1, 2
• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days 1, 2
• Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 1, 2
• Cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions 2

Immediate/anaphylactic penicillin allergy (anaphylaxis, angioedema, respiratory distress, or urticaria within 1 hour):

• Avoid ALL beta-lactams including cephalosporins due to up to 10% cross-reactivity risk 1, 2
• Clindamycin is the preferred alternative: 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days with strong, moderate-quality evidence 1, 2
• Clindamycin has approximately 1% resistance rate among Group A Streptococcus in the United States 2
• Clindamycin is particularly effective in chronic carriers who have failed penicillin treatment 2

Step 2: Alternative Options for Immediate Allergy

Macrolides (use with caution due to resistance):

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 2, 6
• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days 1, 2
• Erythromycin: 20-40 mg/kg/day divided 2-3 times daily (maximum 1 gram per day) for 10 days—less preferred due to gastrointestinal side effects 2, 7

Critical Resistance Considerations

• Macrolide resistance among Group A Streptococcus is approximately 5-8% in the United States but varies geographically and temporally 1, 2
• In areas with high macrolide resistance, clindamycin is more reliable than azithromycin or clarithromycin 2
• Be aware of local resistance patterns before prescribing macrolides 2, 8

Critical Treatment Duration Requirements

All antibiotics require a full 10-day course EXCEPT azithromycin:

• A full 10-day course is essential to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever 1, 2, 3
• Azithromycin is the only exception, requiring only 5 days due to its prolonged tissue half-life 1, 2, 3, 6
• Shortening the course by even a few days results in appreciable increases in treatment failure rates 2
• Therapy can be safely postponed up to 9 days after symptom onset and still prevent acute rheumatic fever 2

Common Pitfalls to Avoid

Do NOT:

• Prescribe once-daily penicillin regimens—they have 22% failure rates versus 8% with divided doses 4, 5
• Use cephalosporins in patients with immediate/anaphylactic penicillin reactions—10% cross-reactivity risk makes this dangerous 1, 2
• Shorten antibiotic courses below 10 days (except azithromycin's 5-day regimen)—this leads to treatment failure and increased rheumatic fever risk 2, 3
• Use azithromycin as first-line therapy—reserve it for documented penicillin allergy when other alternatives cannot be used 2
• Prescribe broader-spectrum cephalosporins (like cefdinir or cefpodoxime) when narrow-spectrum first-generation agents are appropriate—they are more expensive and select for resistant flora 2, 9
• Use trimethoprim-sulfamethoxazole (Bactrim)—it has 50% resistance rates and is not recommended for Group A Streptococcus 2

Do:

• Complete the full 10-day course even if symptoms resolve in 3-4 days—the goal is bacterial eradication and rheumatic fever prevention, not just symptom relief 2
• Distinguish between immediate and non-immediate penicillin allergy—this determines whether cephalosporins can be safely used 2
• Consider intramuscular benzathine penicillin G when adherence to oral therapy is uncertain—single dose ensures compliance 1, 3

Adjunctive Therapy

For symptom management:

• Acetaminophen or NSAIDs (ibuprofen) for moderate to severe symptoms or high fever 2, 3
• Avoid aspirin in children due to Reye syndrome risk 2, 3
• Do NOT use corticosteroids as adjunctive therapy 2

Special Population: Chronic Carriers

• Chronic carriers (asymptomatic patients with persistently positive cultures) generally do NOT require antimicrobial therapy—they are unlikely to spread infection or develop complications 1, 2, 3
• If treatment is indicated for chronic carriers, clindamycin is particularly effective due to its ability to eradicate the organism 2, 3
• Routine post-treatment throat cultures are not recommended for asymptomatic patients who have completed therapy 2