What should an otherwise healthy adult or older child take for acute tonsillitis?

Treatment of Acute Tonsillitis

For an otherwise healthy adult or older child with acute tonsillitis, first confirm bacterial infection with a rapid antigen test or throat culture, then prescribe penicillin V 500 mg twice daily or amoxicillin 500 mg twice daily for a full 10 days if Group A Streptococcus is confirmed. 1

Diagnostic Confirmation First

• Do not prescribe antibiotics without confirming Group A Streptococcus infection via rapid antigen detection test (RADT) or throat culture, because most tonsillitis cases are viral and do not benefit from antibiotics. 1, 2
• Use a clinical scoring system (Centor, McIsaac, or FeverPAIN) to estimate the probability of bacterial infection; scores ≥3 warrant testing. 3, 4
• A positive RADT is diagnostic and requires no backup culture; a negative RADT in children and adolescents should be followed by throat culture. 1

First-Line Antibiotic Treatment (Non-Allergic Patients)

• Penicillin V 500 mg orally twice daily for 10 days is the treatment of choice for adults and children ≥27 kg with confirmed Group A Streptococcus tonsillitis. 1, 5
• Amoxicillin 500 mg orally twice daily for 10 days is equally effective and often preferred due to better palatability and twice-daily dosing that improves adherence. 1, 5
• For children <27 kg, use penicillin V 250 mg twice daily or amoxicillin 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days. 1, 5
• The full 10-day course is mandatory to achieve maximal pharyngeal eradication and prevent acute rheumatic fever, even when symptoms resolve within 3–4 days. 1, 5

Why These Are First-Line

• Zero documented penicillin resistance exists worldwide among Group A Streptococcus. 1, 5
• Narrow antimicrobial spectrum minimizes selection of resistant flora. 1
• Proven efficacy in preventing acute rheumatic fever and suppurative complications. 1, 6
• Lowest cost among all recommended antibiotics. 1

Treatment for Penicillin-Allergic Patients

Non-Immediate (Delayed) Penicillin Allergy

• First-generation cephalosporins are the preferred alternatives with only 0.1% cross-reactivity risk in patients with delayed, mild reactions (e.g., rash occurring >1 hour after exposure). 1, 7
• Cephalexin 500 mg orally twice daily for 10 days in adults; 20 mg/kg twice daily (maximum 500 mg per dose) for 10 days in children. 1, 5
• Cefadroxil 1 g once daily for 10 days is an alternative with comparable efficacy. 1, 7

Immediate/Anaphylactic Penicillin Allergy

• All beta-lactam antibiotics must be avoided because cross-reactivity with cephalosporins can reach 10% in patients with immediate hypersensitivity (anaphylaxis, angioedema, urticaria within 1 hour). 1, 7
• Clindamycin 300 mg orally three times daily for 10 days is the preferred non-beta-lactam alternative, with only ~1% resistance among U.S. Group A Streptococcus isolates and superior eradication even in chronic carriers. 1, 7, 5
• Azithromycin 500 mg once daily for 5 days is an acceptable alternative, but macrolide resistance ranges from 5–8% in the United States and varies geographically. 1, 7
• Clarithromycin 250 mg twice daily for 10 days is another macrolide option with similar resistance concerns. 1, 7

Symptomatic Treatment

• Offer acetaminophen or ibuprofen for moderate-to-severe sore throat, fever, or systemic discomfort. 1, 7
• Avoid aspirin in children due to Reye syndrome risk. 1, 7
• Corticosteroids are not recommended as adjunctive therapy for streptococcal tonsillitis. 1, 7
• If tonsillitis is viral (negative testing), treatment is entirely supportive with analgesia and hydration—no antibiotics. 2, 6

Critical Pitfalls to Avoid

• Do not shorten the antibiotic course below 10 days (except azithromycin's 5-day regimen), as this dramatically increases treatment failure and rheumatic fever risk. 1, 5
• Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions due to the ~10% cross-reactivity risk. 1, 7
• Do not prescribe antibiotics without confirming bacterial infection; most tonsillitis is viral. 1, 2
• Do not use trimethoprim-sulfamethoxazole (Bactrim) for strep throat; it fails to eradicate Group A Streptococcus in 20–25% of cases. 1, 7
• Do not order routine post-treatment throat cultures for asymptomatic patients who completed therapy; reserve testing for special circumstances such as history of rheumatic fever. 1, 7

When to Reassess

• If no clinical improvement occurs within 48–72 hours of starting antibiotics, reassess for non-compliance, alternative diagnosis, or suppurative complications (peritonsillar abscess, parapharyngeal abscess). 1, 3
• Severe signs—difficulty swallowing, drooling, neck tenderness, or unilateral swelling—warrant imaging (contrast-enhanced CT) and may require drainage or IV antibiotics. 1