What are the recommended antibiotics for streptococcal (strep) infections and mononucleosis?

Antibiotic Treatment for Streptococcal Pharyngitis and Mononucleosis

For streptococcal pharyngitis, penicillin or amoxicillin remains the first-line treatment of choice, while antibiotics are not indicated for infectious mononucleosis as it is typically caused by Epstein-Barr virus. 1

Streptococcal Pharyngitis Treatment

First-Line Therapy

• Penicillin remains the treatment of choice for Group A Streptococcal (GAS) pharyngitis due to its proven efficacy, safety, narrow spectrum, and low cost 1
• Amoxicillin is often used in place of penicillin V for young children primarily due to better taste acceptance, with equivalent efficacy 1
• The standard duration for penicillin/amoxicillin therapy is 10 days to achieve maximal pharyngeal eradication of GAS 1

Dosing for Streptococcal Pharyngitis

• For adults: Penicillin V 250 mg every 6 hours or 500 mg every 12 hours for 10 days 1
• For children: Penicillin V 50 mg/kg/day divided into 4 doses (maximum = 2,000 mg per day) for 10 days 1
• For children: Amoxicillin 50 mg/kg once daily (maximum = 1,000 mg) for 10 days 1
• Intramuscular benzathine penicillin G is preferred for patients unlikely to complete a full 10-day course of oral therapy 1

Alternative Therapy for Penicillin-Allergic Patients

• For non-anaphylactic penicillin allergy: First-generation cephalosporins (e.g., cephalexin) for 10 days 1, 2
  • Cephalexin dosing: Adults 500 mg every 12 hours; children 25-50 mg/kg/day in divided doses 3
• For severe/immediate penicillin allergy: 1, 2
  • Clindamycin: 7 mg/kg per dose three times daily (maximum = 300 mg per dose) for 10 days
  • Macrolides (with awareness of potential resistance):
    • Erythromycin: 20-40 mg/kg/day divided 2-3 times daily for 10 days
    • Clarithromycin: 7.5 mg/kg twice daily (maximum = 250 mg per dose) for 10 days
    • Azithromycin: 12 mg/kg once daily (maximum = 500 mg) for 5 days 1, 4

Important Considerations

• Macrolide resistance in GAS varies geographically and temporally, with approximately 5-8% resistance rates in the US 1, 2
• Azithromycin is the only antibiotic approved for a shorter 5-day course due to its prolonged tissue half-life 2, 4, 5
• Twice-daily dosing of penicillin has been shown to be as effective as more frequent dosing regimens, which may improve compliance 6
• Penicillin failure rates have increased over time from 2-10% in the 1970s to approximately 30% in more recent years, often due to poor compliance with the 10-day regimen 7

Infectious Mononucleosis Treatment

• Antibiotics are not indicated for infectious mononucleosis as it is typically caused by Epstein-Barr virus, not bacteria 1
• If a patient with mononucleosis is mistakenly prescribed amoxicillin, they may develop a characteristic rash that can be misinterpreted as a drug allergy 2

Management of Recurrent or Persistent Streptococcal Pharyngitis

• For chronic carriers or recurrent infections, consider: 1
  • Clindamycin: 20-30 mg/kg/day in three doses (maximum = 300 mg per dose) for 10 days
  • Amoxicillin/clavulanate: 40 mg amoxicillin/kg/day in three doses for 10 days
  • Penicillin plus rifampin: Penicillin for 10 days with rifampin added during the last 4 days

Adjunctive Therapy

• Acetaminophen or NSAIDs may be used for moderate to severe symptoms or high fever 1, 2
• Aspirin should be avoided in children due to the risk of Reye syndrome 1, 2
• Corticosteroids are not recommended as adjunctive therapy 1, 2

Testing and Follow-up

• Routine post-treatment throat cultures are not recommended for asymptomatic patients who have completed therapy 1
• Testing or treatment of asymptomatic household contacts is not routinely recommended 1