Augmentin Dosing for a 13-Year-Old with Mastitis (45 kg)
For a 13-year-old weighing 45 kg with mastitis, prescribe Augmentin 875 mg/125 mg tablet twice daily (every 12 hours) for 7–10 days, as this patient meets the adult dosing threshold of ≥40 kg. 1, 2
Weight-Based Dosing Threshold
- Children weighing ≥40 kg should be dosed according to adult recommendations rather than pediatric weight-based calculations. 1, 2
- The FDA label explicitly states that "pediatric patients weighing 40 kg or more should be dosed according to adult recommendations." 2
- At exactly 40 kg or above, the transition to adult formulations and dosing regimens is appropriate for all indications. 3
Adult Dosing for Skin and Soft-Tissue Infections
- For respiratory tract infections and more severe infections, the FDA-approved adult dose is 875 mg/125 mg every 12 hours or 500 mg/125 mg every 8 hours. 2
- Mastitis, as a soft-tissue infection, warrants the higher-strength formulation (875 mg/125 mg twice daily) to ensure adequate tissue penetration and coverage of β-lactamase-producing organisms. 2
Treatment Duration
- Standard treatment duration for soft-tissue infections is 7–10 days, extendable to 14 days based on clinical response. 1
- Continue therapy for at least 48–72 hours after complete resolution of fever and local signs of infection (erythema, warmth, tenderness). 1, 3
Expected Clinical Response
- Clinical improvement should be evident within 48–72 hours of initiating therapy, including reduction in pain, erythema, and systemic symptoms. 1, 3, 4
- If no improvement or worsening occurs after 72 hours, reassess for complications (abscess formation requiring drainage), consider atypical pathogens, or evaluate for alternative diagnoses. 1, 3
Critical Formulation Note
- Do NOT use the 250 mg/125 mg tablet formulation until the child weighs at least 40 kg, due to different amoxicillin-to-clavulanate ratios (250/125 versus 250/62.5 in pediatric chewable tablets). 2
- The 875 mg/125 mg tablet is the appropriate adult-strength formulation for patients ≥40 kg. 2
Abscess Management Consideration
- If a fluctuant mass or abscess is present, incision and drainage is the primary treatment; antibiotics alone are insufficient for draining purulent collections. 1
- Augmentin serves as adjunctive therapy to prevent spread of cellulitis surrounding an abscess but does not replace surgical drainage. 1
Penicillin Allergy Alternatives
- For non-anaphylactic penicillin allergy, second- or third-generation cephalosporins (cefdinir, cefuroxime) are safe alternatives with negligible cross-reactivity risk. 1, 3
- For IgE-mediated (Type I) reactions, clindamycin 300–450 mg three times daily is the preferred alternative for skin and soft-tissue infections. 1
Common Pitfall to Avoid
- Do not underdose by using pediatric weight-based calculations (e.g., 90 mg/kg/day = 4,050 mg/day) when the patient meets the adult weight threshold; this leads to unnecessarily high doses and increased adverse effects without additional benefit. 1, 3
- The adult dose of 875 mg twice daily (1,750 mg/day total amoxicillin) is appropriate and sufficient for this 45 kg adolescent. 2