What antibiotics are used to treat bacterial tonsillitis?

Antibiotic Treatment for Bacterial Tonsillitis

First-Line Treatment

Penicillin V (phenoxymethylpenicillin) or amoxicillin for 10 days is the first-line antibiotic treatment for confirmed bacterial tonsillitis caused by Group A Streptococcus. 1, 2, 3

Preferred First-Line Regimens

• Penicillin V remains the gold standard with five decades of proven efficacy and no documented resistance development 3

  • Pediatric dosing: 250 mg two or three times daily for 10 days 3
  • Adult dosing: 250 mg four times daily OR 500 mg twice daily for 10 days 3, 4
  • Universal susceptibility of Group A Streptococcus makes this the most reliable choice 1

• Amoxicillin is preferred in younger children due to better taste and suspension availability 3

  • Pediatric dosing: 50 mg/kg once daily (maximum 1,000 mg) for 10 days 3
  • Adult dosing: 250 mg four times daily OR 500 mg twice daily for 10 days 3
  • Achieves peak blood levels of 5.5-7.5 mcg/mL within 1-2 hours 5

• Penicillin G benzathine (intramuscular) is a single-dose alternative for compliance concerns 3

  • 600,000 units for patients <27 kg 3
  • 1,200,000 units for patients ≥27 kg 3

Critical Treatment Duration

• The full 10-day course is essential for penicillin and amoxicillin to maximize bacterial eradication and prevent rheumatic fever 2, 3
• Short courses (5 days) of standard-dose penicillin are less effective and should be avoided 2
• Antibiotics reduce rheumatic fever risk by 73% (RR 0.27) and peritonsillar abscess risk by 85% (RR 0.15) 3

Second-Line Treatment Options

For Penicillin-Allergic Patients (Non-Anaphylactic)

• Cephalexin is the preferred second-choice antibiotic based on lower relapse rates and narrow spectrum 2, 3
  • Dosing: 20 mg/kg per dose twice daily (maximum 500 mg per dose) for 10 days 3
  • First-generation cephalosporins (cefadroxil is also acceptable) for 10 days 2

For Severe Penicillin Allergy (Anaphylactic)

• Clarithromycin should be used when severe penicillin allergy exists 2, 3

  • Pediatric dosing: 7.5 mg/kg per dose twice daily (maximum 250 mg per dose) for 10 days 3
  • Major caveat: Effectiveness is significantly compromised in areas with high macrolide resistance 3, 6
  • In one study, clarithromycin failed to eradicate 81-86% of resistant isolates 6

• Azithromycin is an alternative macrolide with more convenient dosing 2, 7

  • Pediatric dosing: 12 mg/kg once daily for 5 days 8
  • Achieved 95% bacteriologic eradication at Day 14 versus 73% with penicillin V in FDA trials 8
  • Once-daily dosing improves compliance 7

• Clindamycin is another option for severe allergy 2, 3

  • Dosing: 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days 3

Treatment Failures and Recurrent Tonsillitis

When Initial Penicillin Therapy Fails

• Amoxicillin-clavulanate (Augmentin) achieves higher eradication rates in penicillin treatment failures 1

  • Adult dosing: 500 mg amoxicillin/125 mg clavulanate three times daily for 10 days 1
  • Pediatric dosing: 45 mg/kg/day of amoxicillin component divided into 2-3 doses 1
  • High-dose pediatric regimen: 80-90 mg/kg/day amoxicillin with 6.4 mg/kg/day clavulanate in 2 divided doses for children with risk factors 1
  • Broader coverage addresses beta-lactamase producing organisms 1, 9

• Reassess patients showing no improvement within 48-72 hours and consider switching to amoxicillin-clavulanate 1

For Documented Recurrent GAS Tonsillitis

• Clindamycin is recommended for recurrence within 2 weeks of completing standard therapy 2

  • Dosing: 20-30 mg/kg/day in 3 doses (maximum 300 mg/dose) for 10 days 2

• Alternative regimens include amoxicillin-clavulanate at 40 mg amoxicillin/kg/day in 3 doses (maximum 2000 mg/day) for 10 days 2

• Penicillin with rifampin: Penicillin V 50 mg/kg/day in 4 doses for 10 days plus rifampin 20 mg/kg/day in 1 dose for the last 4 days 2

Critical Pitfalls to Avoid

• Never treat without confirming GAS infection through rapid antigen detection testing (RADT) or throat culture 2
• Do not use inadequate treatment duration (<10 days) for penicillin, amoxicillin, or clarithromycin, as this increases treatment failure risk 2, 3
• Check local macrolide resistance patterns before prescribing clarithromycin or azithromycin, as resistance is geographically variable 3, 6
• Avoid routine follow-up cultures for asymptomatic patients who completed appropriate therapy 2
• Consider chronic GAS carriage in patients with recurrent positive tests, as up to 20% of school-age children may be asymptomatic carriers experiencing viral pharyngitis 2
• Do not prescribe broad-spectrum antibiotics when narrow-spectrum penicillins are effective for confirmed GAS 2

Diagnostic Confirmation Required

• Antibiotics should only be prescribed for confirmed bacterial cases through RADT and/or throat culture 2
• Bacterial tonsillitis is characterized by sudden onset sore throat, fever >38°C, tonsillar exudates, tender anterior cervical lymphadenopathy, and absence of cough 2
• Viral tonsillitis lacks high fever, tonsillar exudate, and cervical lymphadenopathy 2