Amoxicillin Dosing for Streptococcal Pharyngitis
For streptococcal pharyngitis, amoxicillin should be dosed at 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for a full 10-day course. 1
Standard Dosing Regimens
Once-daily dosing is the preferred regimen due to enhanced adherence while maintaining equivalent efficacy to traditional multi-dose penicillin therapy:
- 50 mg/kg once daily (maximum 1000 mg/day) for 10 days 1, 2
- This regimen has strong, high-quality evidence demonstrating non-inferiority to twice-daily dosing 3
- The American Heart Association endorses once-daily amoxicillin as an acceptable alternative to penicillin 4
Twice-daily dosing remains an acceptable alternative:
- 25 mg/kg per dose twice daily (maximum 500 mg per dose) for 10 days 1, 2
- Both regimens achieve comparable bacteriologic cure rates of 79-88% 5, 3
Why Amoxicillin is Recommended
Amoxicillin is often preferred over penicillin V, particularly in young children, primarily due to better palatability of the suspension formulation 1. The efficacy is equivalent to penicillin, with the added benefit of once-daily dosing that may improve adherence 1, 4. Penicillin and amoxicillin remain the drugs of choice due to their narrow spectrum, proven safety, lack of resistance (penicillin-resistant Group A Streptococcus has never been documented), and low cost 1.
Critical Treatment Duration
A full 10-day course is mandatory regardless of symptom resolution to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever 1, 6. Symptoms typically resolve within 3-4 days without treatment, but completing the full course is essential for preventing complications 6. Therapy can be safely postponed up to 9 days after symptom onset and still prevent acute rheumatic fever 6.
Alternatives for Penicillin-Allergic Patients
For patients with non-immediate (non-anaphylactic) penicillin allergy:
- First-generation cephalosporins are preferred: cephalexin 20 mg/kg per dose twice daily (maximum 500 mg per dose) or cefadroxil 30 mg/kg once daily (maximum 1 gram) for 10 days 1, 6
- Cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions 6
For patients with immediate/anaphylactic penicillin allergy (anaphylaxis, angioedema, respiratory distress, or urticaria within 1 hour):
- Clindamycin 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days is the preferred choice 1, 6
- Clindamycin has approximately 1% resistance rate in the United States and demonstrates high efficacy even in chronic carriers 6
- Azithromycin 12 mg/kg once daily (maximum 500 mg) for 5 days is an acceptable alternative 1, 6
- Macrolide resistance is 5-8% in the United States and varies geographically 1, 6
- Clarithromycin 7.5 mg/kg per dose twice daily (maximum 250 mg per dose) for 10 days is also acceptable 1, 6
Up to 10% of patients with immediate hypersensitivity to penicillin may have cross-reactivity with cephalosporins, so all beta-lactams should be avoided in this population 1, 6.
Common Pitfalls to Avoid
Do not shorten the treatment course below 10 days (except for azithromycin's 5-day regimen) as this results in appreciable increases in treatment failure rates and risk of acute rheumatic fever 1, 6. Even shortening by a few days significantly compromises bacterial eradication 6.
Do not use broad-spectrum cephalosporins (cefaclor, cefuroxime, cefixime, cefdinir, cefpodoxime) when narrow-spectrum agents are appropriate, as they are more expensive and more likely to select for antibiotic-resistant flora 1.
Do not use tetracyclines, sulfonamides, trimethoprim-sulfamethoxazole, or older fluoroquinolones (ciprofloxacin) as they are ineffective for Group A Streptococcus eradication 1.
Do not prescribe azithromycin as first-line therapy when penicillin or amoxicillin can be used, as this unnecessarily broadens the antibiotic spectrum and contributes to resistance 6. Azithromycin should be reserved for patients with documented immediate penicillin allergy who cannot tolerate cephalosporins or clindamycin 6.
Do not routinely perform post-treatment throat cultures in asymptomatic patients who have completed therapy, as this is not recommended 6. Testing should only be considered in special circumstances, such as patients with a history of rheumatic fever 6.
Adjunctive Therapy
Acetaminophen or NSAIDs (ibuprofen) should be considered for moderate to severe symptoms or control of high fever 1, 6. Aspirin must be avoided in children due to the risk of Reye syndrome 1, 6. Corticosteroids are not recommended as adjunctive therapy 1, 6.