What is the dose of antibiotic (anti-bacterial medication) for streptococcal (strep) infections?

Antibiotic Dosing for Streptococcal Infections

For streptococcal pharyngitis, penicillin V should be administered at 500 mg 2-3 times daily for adults or 250 mg 2-3 times daily for children for 10 days. 1

First-Line Treatment Options

Oral Penicillin V (First Choice)

• Adults: 500 mg 2-3 times daily for 10 days
• Children: 250 mg 2-3 times daily for 10 days
• The 10-day duration is critical to prevent acute rheumatic fever 1

Amoxicillin (Alternative First-Line)

• Children under 40 kg: 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days
• Adults and children over 40 kg: 500 mg every 8 hours or 875 mg every 12 hours for 10 days 1, 2
• Particularly useful for young children due to better taste and liquid formulation availability

Treatment for Penicillin-Allergic Patients

For patients with penicillin allergy, the following alternatives are recommended:

• Cephalexin: 20 mg/kg twice daily (maximum 500 mg per dose) for 10 days
• Clindamycin: 7 mg/kg three times daily (maximum 300 mg per dose) for 10 days
• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1

Important Clinical Considerations

1. Treatment Duration:

   • A full 10-day course is essential for penicillins and most alternatives
   • This duration is specifically recommended to prevent acute rheumatic fever 1, 2

2. Contagiousness:

   • Patients are considered non-contagious after 24 hours of antibiotic therapy
   • Symptoms typically improve within 24-48 hours after starting treatment 1

3. Compliance Issues:

   • Poor compliance is a major cause of treatment failure
   • While shorter courses (≤5 days) of cephalosporins have shown efficacy in some studies, the standard 10-day treatment remains recommended for penicillins 1, 3

4. Treatment Failure:

   • For recurrence shortly after treatment completion, consider retreatment with the same antibiotic or intramuscular benzathine penicillin G 1

Antimicrobial Stewardship Considerations

Despite some studies showing efficacy of shorter courses of cephalosporins or macrolides, penicillin V remains the first-line treatment due to:

• Narrow spectrum of activity
• Low cost
• Long history of safety and efficacy
• No significant resistance development among Group A Streptococcus 1, 3

Macrolides and cephalosporins are classified as "Highest Priority Critically Important Antimicrobials" and should be reserved for patients with true penicillin allergy 3.