Amoxicillin Dosing for Group B Streptococcus Abscess
For a Group B Streptococcus abscess, surgical incision and drainage is the primary treatment, with amoxicillin 500 mg orally three times daily (or 875 mg twice daily) for adults as adjunctive antibiotic therapy for 7-14 days depending on severity and clinical response. 1
Primary Treatment Approach
Surgical drainage is the mainstay of abscess management and must be performed first. 1 Antibiotic therapy alone is insufficient for abscess treatment, as antibiotics cannot adequately penetrate purulent collections. 1
Standard Amoxicillin Dosing
Adults
- Mild to moderate infections: 500 mg orally three times daily (every 8 hours) 1, 2
- Severe infections: 875 mg orally twice daily (every 12 hours) or 500 mg every 8 hours 2
- Duration: Continue for minimum 48-72 hours beyond symptom resolution, typically 7-14 days total 2
Pediatric Patients (≥3 months and <40 kg)
- Mild to moderate infections: 25 mg/kg/day divided every 12 hours or 20 mg/kg/day divided every 8 hours 2
- Severe infections: 45 mg/kg/day divided every 12 hours or 40 mg/kg/day divided every 8 hours 2
Renal Impairment Adjustments
Dose reduction is required for severe renal impairment to prevent drug accumulation and toxicity. 2
- GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours (depending on severity) 2
- GFR <10 mL/min: 500 mg or 250 mg every 24 hours 2
- Hemodialysis: 500 mg or 250 mg every 24 hours, with additional dose during and after dialysis 2
- Important: Do NOT use the 875 mg dose in patients with GFR <30 mL/min 2
Critical Clinical Considerations
Group B Streptococcus remains universally susceptible to penicillins worldwide, making amoxicillin an excellent choice. 3 However, one case report documented penicillin-tolerant Group B Streptococcus in a prosthetic joint infection that required addition of gentamicin for synergy. 4
For complicated or deep-seated abscesses (such as those involving prosthetic material, bone, or showing systemic toxicity), consider intravenous therapy initially: 1
- Ampicillin 2 g IV every 4-6 hours 5
- Consider adding gentamicin for synergistic killing if tolerance is suspected or infection is severe 4
Alternative Agents for Penicillin Allergy
For non-severe penicillin allergy (no history of anaphylaxis, angioedema, respiratory distress, or urticaria):
- Cefazolin 2 g IV initially, then 1 g IV every 8 hours 6, 3
- Note: Approximately 10% cross-reactivity exists between penicillins and cephalosporins 6, 3
For severe penicillin allergy:
- Clindamycin 300-450 mg orally three times daily or 600 mg IV every 8 hours 1, 3
- Obtain susceptibility testing, as resistance to clindamycin is increasing 3
Common Pitfalls to Avoid
Do not treat with antibiotics alone without drainage - this leads to treatment failure regardless of antibiotic choice. 1
Do not underdose or use inadequate duration - continue therapy for at least 48-72 hours beyond clinical improvement to prevent recurrence. 2
Do not forget to adjust for renal function - failure to reduce dose in severe renal impairment increases toxicity risk, particularly in elderly patients who commonly have decreased renal function. 2
Do not assume all penicillin allergies are true IgE-mediated reactions - verify allergy history, as many reported allergies are not genuine hypersensitivity and patients may safely receive penicillins. 6, 3
Take amoxicillin at the start of meals to minimize gastrointestinal intolerance. 2