What are the recommended antibiotics and dosing for acute Group A streptococcal pharyngitis in an otherwise healthy 18‑year‑old female?

Recommended Antibiotics and Dosing for Strep Throat in an 18-Year-Old Female

For an otherwise healthy 18-year-old female with confirmed Group A streptococcal pharyngitis, prescribe oral penicillin V 500 mg twice daily (or 250 mg four times daily) for a full 10 days, or alternatively amoxicillin 500 mg twice daily for 10 days. 1, 2, 3

First-Line Treatment: Penicillin or Amoxicillin

• Penicillin V remains the drug of choice due to its proven efficacy, narrow antimicrobial spectrum, excellent safety profile, modest cost, and the complete absence of documented penicillin resistance in Group A Streptococcus anywhere in the world. 1, 4

• Adult dosing for penicillin V: 500 mg orally twice daily OR 250 mg four times daily for 10 days. 1, 2, 3

• Adult dosing for amoxicillin: 500 mg orally twice daily for 10 days (or 1000 mg once daily as an alternative). 1, 2, 4

• The full 10-day course is mandatory to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever, even if symptoms resolve within 3–4 days. 1, 5, 2

• Intramuscular benzathine penicillin G 1.2 million units as a single dose is an excellent alternative when adherence to a 10-day oral regimen is uncertain. 1, 2, 4

Alternative Antibiotics for Penicillin Allergy

For Non-Immediate (Delayed) Penicillin Allergy

• First-generation cephalosporins are the preferred alternatives with strong, high-quality evidence supporting their use. 1, 5

• Cephalexin 500 mg orally twice daily for 10 days is the recommended first-generation cephalosporin. 1, 5, 2

• Cefadroxil 1 gram orally once daily for 10 days is an acceptable alternative. 1, 5, 2

• The cross-reactivity risk with first-generation cephalosporins is only 0.1% in patients with non-severe, delayed penicillin reactions (e.g., mild rash days after exposure). 5

For Immediate/Anaphylactic Penicillin Allergy

• All beta-lactam antibiotics must be avoided in patients with immediate hypersensitivity reactions (anaphylaxis, angioedema, urticaria within 1 hour, bronchospasm) due to up to 10% cross-reactivity risk with cephalosporins. 1, 5

• Clindamycin 300 mg orally three times daily for 10 days is the preferred choice for immediate/anaphylactic penicillin allergy, with only ~1% resistance among Group A Streptococcus in the United States and demonstrated high efficacy even in chronic carriers. 1, 5, 2

• Azithromycin 500 mg orally on day 1, then 250 mg daily for days 2–5 (total 5 days) is an acceptable alternative, though macrolide resistance rates are 5–8% in the United States and vary geographically. 1, 5, 2

• Clarithromycin 250 mg orally twice daily for 10 days is another macrolide option with similar resistance concerns as azithromycin. 1, 5, 2

• Azithromycin is the only antibiotic requiring just 5 days due to its prolonged tissue half-life; all other antibiotics require the full 10-day course. 1, 5

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 rates and the risk of acute rheumatic fever. 1, 5

• Do not prescribe cephalosporins to patients with immediate/anaphylactic penicillin reactions due to the 10% cross-reactivity risk. 1, 5

• Do not use trimethoprim-sulfamethoxazole (Bactrim) for strep throat, as sulfonamides fail to eradicate Group A Streptococcus in 20–25% of cases. 5

• Do not use tetracyclines or older fluoroquinolones due to high resistance rates and limited activity against Group A Streptococcus. 5, 4

• Do not prescribe broad-spectrum cephalosporins (cefuroxime, cefdinir, cefpodoxime) when narrow-spectrum first-generation agents are appropriate, as they are more expensive and promote antibiotic-resistant flora. 5

Adjunctive Symptomatic Treatment

• Acetaminophen or NSAIDs (ibuprofen) can be used for moderate to severe symptoms or high fever. 1, 5

• Aspirin must be avoided in children and adolescents due to Reye syndrome risk (though at 18 years this risk is minimal). 1, 5

• Corticosteroids are not recommended as adjunctive therapy. 1, 5

Post-Treatment Considerations

• Routine follow-up throat cultures or rapid tests are not recommended for asymptomatic patients who have completed therapy. 1, 5

• Testing should only be considered in special circumstances, such as patients with a personal or family history of rheumatic fever. 1

• Patients are generally non-contagious after 24 hours of antibiotic therapy. 2