What are the recommended antibiotics for treating peritonsillar abscess?

Antibiotic Treatment for Peritonsillar Abscess

For peritonsillar abscess, drainage (needle aspiration or incision) is the primary treatment, followed by antibiotics effective against Group A Streptococcus and oral anaerobes—specifically penicillin combined with metronidazole, or clindamycin as a single-agent alternative. 1, 2, 3

Primary Treatment Approach

• Drainage is mandatory and must be performed first—needle aspiration remains the gold standard for both diagnosis and treatment of peritonsillar abscess. 2
• Antibiotics alone will fail without adequate drainage, regardless of the antibiotic chosen. 4
• After drainage, antibiotic therapy targeting the polymicrobial nature of the infection (aerobic and anaerobic bacteria) must be initiated immediately. 1, 2

First-Line Antibiotic Regimens

Preferred Combination Therapy

• Penicillin (phenoxymethylpenicillin 4.5 million units per day divided into doses) PLUS metronidazole (500 mg every 8 hours or 1500 mg total daily) is the recommended first-line regimen. 3, 5
• This combination provides coverage against Group A Streptococcus (the predominant organism) and oral anaerobes (including Bacteroides species). 1, 3
• Studies demonstrate complete recovery in all patients treated with this combination after drainage. 3

Alternative Single-Agent Therapy

• Clindamycin (300-450 mg orally three times daily) is the preferred single-agent alternative when combination therapy cannot be used. 2, 5
• Clindamycin provides excellent coverage against both aerobic streptococci and anaerobic bacteria, making it particularly useful as monotherapy. 4, 5
• If penicillin-metronidazole treatment is ineffective, switch to broad-spectrum clindamycin. 5

Other Acceptable Options

• Cephalosporins can be used as alternatives, though they require consideration of anaerobic coverage. 2
• Amoxicillin-clavulanate provides both aerobic and anaerobic coverage in a single agent. 6

Bacteriology Considerations

• Peritonsillar abscess is a polymicrobial infection with mixed aerobic and anaerobic flora in approximately 50% of cases. 3
• Group A Streptococcus is the predominant organism isolated. 1, 3
• Staphylococcus aureus is the second most common pathogen, and notably, all S. aureus isolates show resistance to penicillin. 7
• Anaerobic bacteria (particularly Bacteroides and Peptostreptococcus species) are present in 50-75% of cases. 3, 5
• Other organisms include Haemophilus influenzae, Pseudomonas aeruginosa, E. coli, and Enterococcus species. 7

Treatment Duration and Monitoring

• Continue antibiotics for 5-10 days based on clinical response. 4
• Clinical improvement should be evident within 3-5 days after drainage and antibiotic initiation. 6
• If no improvement occurs within this timeframe, re-evaluate for inadequate drainage, resistant organisms, or alternative diagnoses. 6

Critical Pitfalls to Avoid

• Never rely on antibiotics alone without drainage—this approach will fail regardless of antibiotic selection. 4, 2
• Do not use penicillin monotherapy if Staphylococcus aureus is suspected or isolated, as resistance is universal. 7
• Avoid neglecting anaerobic coverage—anaerobes are present in the majority of cases and require specific antimicrobial activity. 3, 5
• Bacteriologic cultures are unnecessary on initial presentation for routine cases, but should be obtained if treatment fails or in severe infections. 4, 3, 5

Adjunctive Therapy

• Maintain adequate hydration and provide pain control as supportive measures. 1
• Corticosteroids may help reduce symptoms and speed recovery, though this is adjunctive to drainage and antibiotics. 1