What is the recommended dosage of Augmentin (amoxicillin-clavulanate) for a 13-year-old patient weighing 90 pounds with a suspected bacterial infection?

Augmentin Dosing for a 13-Year-Old Weighing 90 Pounds

For a 13-year-old weighing 90 pounds (41 kg), Augmentin 500 mg is significantly underdosed and should not be used; the correct dosing depends on the infection type but typically requires 45-90 mg/kg/day of the amoxicillin component divided into 2-3 doses. 1, 2

Weight-Based Dosing Calculation

This patient weighs 41 kg, which places them above the 40 kg threshold where adult dosing typically applies. However, the specific infection type determines the appropriate regimen 3:

For Mild to Moderate Infections (Ear/Nose/Throat, Skin, Genitourinary)

• Standard dose: 500 mg every 12 hours OR 250 mg every 8 hours 3
• This provides approximately 25 mg/kg/day, which is appropriate for uncomplicated infections 1

For Severe Infections or Lower Respiratory Tract Infections

• High-dose regimen: 875 mg every 12 hours OR 500 mg every 8 hours 3
• This provides approximately 45 mg/kg/day, necessary for adequate coverage 1, 2

For High-Risk Situations (Recent Antibiotic Use, Daycare, Resistant Organisms)

• Maximum dose: 90 mg/kg/day of amoxicillin component divided into 2 doses 1, 2
• For this 41 kg patient: approximately 1,845 mg twice daily (not exceeding 4,000 mg/day maximum) 1, 2

Why "Augmentin 500" Is Problematic

The prescription "Augmentin 500" is ambiguous and likely inadequate because:

• It doesn't specify the dosing frequency (every 8 hours vs every 12 hours) 3
• 500 mg once or twice daily provides only 12-24 mg/kg/day, which is subtherapeutic for most infections 1, 2
• The formulation ratio (amoxicillin:clavulanate) isn't specified, though 500/125 mg is standard 2

Infection-Specific Recommendations

Community-Acquired Pneumonia

• Preferred: 875 mg every 12 hours (45 mg/kg/day) for standard cases 1, 3
• High-dose: 90 mg/kg/day in 2 doses if risk factors present (recent antibiotics, high resistance area, severe illness) 1, 2
• Duration: 10 days 1, 2

Acute Bacterial Sinusitis

• Standard: 875 mg every 12 hours for 10-14 days 2
• High-dose: 90 mg/kg/day in 2 doses if recent antibiotic use or severe symptoms 2

Skin and Soft Tissue Infections

• Standard: 500 mg every 12 hours for mild infections 4, 3
• Severe: 875 mg every 12 hours 4, 3

Urinary Tract Infections

• Dose: 500 mg every 12 hours for 7-14 days 5, 3
• Alternative agents may be preferred based on local resistance patterns 5

Critical Dosing Considerations

Treatment duration matters: Continue therapy for a minimum of 48-72 hours beyond symptom resolution, with at least 10 days for streptococcal infections to prevent rheumatic fever 3

Clinical improvement timeline: Patients should show improvement within 48-72 hours; if not, reevaluation is necessary 1, 2

Administration: Take at the start of meals to minimize gastrointestinal intolerance 3

Common Pitfalls to Avoid

• Underdosing: Using 500 mg once or twice daily provides inadequate coverage for most infections in this weight range 1, 2
• Wrong formulation: Standard-dose Augmentin (45 mg/kg/day) may fail against resistant organisms when high-dose therapy (90 mg/kg/day) is indicated 2
• Inadequate duration: Stopping antibiotics when symptoms improve but before completing the full course increases treatment failure risk 1, 3
• Missing risk factors: Failing to identify recent antibiotic use, daycare attendance, or incomplete vaccination status that warrant high-dose therapy 2

Practical Prescription

For most respiratory infections in this patient:

• Augmentin 875/125 mg orally every 12 hours for 10 days 1, 2, 3

For severe infections or resistant organism risk:

• Augmentin 875/125 mg orally every 8 hours (providing ~64 mg/kg/day) OR consider alternative high-dose formulations 1, 2