What is the recommended treatment for an adult patient with strep (streptococcal) pharyngitis?

Treatment of Streptococcal Pharyngitis in Adults

For adults with confirmed Group A streptococcal pharyngitis, penicillin V 500 mg orally twice daily or amoxicillin 500 mg orally twice daily for 10 days is the recommended first-line treatment. 1, 2

Confirm the Diagnosis First

Before prescribing antibiotics, laboratory confirmation is essential because only 5-15% of adult pharyngitis cases are actually caused by Group A Streptococcus, yet over 60% receive unnecessary antibiotics 3, 4:

• Use the modified Centor criteria to determine who needs testing: fever by history, tonsillar exudates, tender anterior cervical adenopathy, and absence of cough 2, 5
• Patients with fewer than 2 Centor criteria should not be tested or treated 2, 4
• For patients with 2-3 criteria, perform a rapid antigen detection test (RADT) and only treat if positive 2, 4
• Unlike in children, negative RADT in adults does not require confirmatory throat culture 2, 3

First-Line Antibiotic Treatment

Penicillin or amoxicillin remains the drug of choice based on proven efficacy, narrow spectrum, safety profile, and low cost 1, 2:

• Penicillin V: 250 mg four times daily OR 500 mg twice daily for 10 days 1, 2
• Amoxicillin: 500 mg twice daily for 10 days 1, 2
• Benzathine penicillin G: 1.2 million units intramuscular as a single dose (preferred when compliance is uncertain) 1, 2

The full 10-day course is essential to achieve maximal pharyngeal eradication and prevent acute rheumatic fever, even though symptoms typically resolve in 3-4 days 1, 2, 6. Therapy can be safely initiated up to 9 days after symptom onset and still prevent rheumatic fever 1, 2.

Treatment for Penicillin-Allergic Patients

Non-Anaphylactic Penicillin Allergy

First-generation cephalosporins are the preferred alternative with strong, high-quality evidence 1, 7:

• Cephalexin: 500 mg orally twice daily for 10 days 1, 7
• Cefadroxil: 1 gram orally once daily for 10 days 1, 7
• Cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions 7

Immediate/Anaphylactic Penicillin Allergy

All beta-lactam antibiotics must be avoided due to up to 10% cross-reactivity risk 1, 7. Use these alternatives:

• Clindamycin (preferred): 300 mg orally three times daily for 10 days 1, 7

  • Only ~1% resistance rate among Group A Streptococcus in the United States 7
  • Particularly effective in chronic carriers and treatment failures 7

• Azithromycin: 500 mg orally once daily for 5 days 1, 7

  • Only antibiotic requiring just 5 days due to prolonged tissue half-life 1, 7
  • 5-8% macrolide resistance in the United States, varies geographically 1, 7, 8
  • No data proving it prevents rheumatic fever 8

• Clarithromycin: 250 mg orally twice daily for 10 days 1, 7

  • Same resistance concerns as azithromycin 1, 7

Critical Treatment Considerations

All antibiotics except azithromycin require a full 10-day course to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 1, 7, 6. Shortening the course by even a few days dramatically increases treatment failure rates and rheumatic fever risk 7.

Why Penicillin Remains First-Line

• No documented penicillin resistance in Group A Streptococcus anywhere in the world 7
• Narrow spectrum minimizes selection pressure for antibiotic-resistant flora 1, 9
• Proven efficacy in preventing rheumatic fever for nearly 40 years 10, 9
• Lowest cost option 1, 2

Symptomatic Management

Every patient should receive appropriate symptomatic care regardless of antibiotic use 2, 3:

• NSAIDs or acetaminophen for moderate to severe symptoms or high fever (strong, high-quality evidence) 1, 2, 5
• Throat lozenges and salt water gargles for temporary relief 2, 3
• Avoid aspirin in children due to Reye syndrome risk 1
• Corticosteroids are not recommended 1, 2

Antibiotics shorten symptom duration by only 1-2 days, with a number needed to treat of 6 at 3 days and 21 at 1 week 2, 3. The primary justification for treatment is preventing complications: acute rheumatic fever, peritonsillar abscess, and spread to close contacts 2, 3.

Common Pitfalls to Avoid

• Do not prescribe antibiotics without laboratory confirmation - only 5-15% of adult pharyngitis is streptococcal 3, 4
• Do not use cephalosporins in patients with anaphylaxis, angioedema, or immediate urticaria to penicillin - 10% cross-reactivity risk 1, 7
• Do not shorten antibiotic courses below 10 days (except azithromycin's 5-day regimen) - increases treatment failure and rheumatic fever risk 1, 7, 6
• Do not treat chronic carriers who have repeated viral infections with positive tests - they are at low risk for complications and transmission 2, 3
• Do not routinely perform post-treatment testing in asymptomatic patients 1, 2
• Do not prescribe broad-spectrum cephalosporins when narrow-spectrum first-generation agents are appropriate - more expensive and select for resistant flora 7

When to Reevaluate

Patients with worsening symptoms after appropriate antibiotic initiation or symptoms lasting 5 days after treatment starts should be reevaluated for complications such as peritonsillar abscess, parapharyngeal abscess, or Lemierre syndrome 2, 11.