What is the appropriate Augmentin (amoxicillin + clavulanate) dosage for a child weighing 42 lb (≈19 kg)?

Augmentin Dosing for 42 lb Child

For a child weighing 42 lbs (19 kg), give Augmentin 125 mg/5 mL suspension at 8.5 mL twice daily (providing approximately 90 mg/kg/day of amoxicillin). This assumes you're treating a condition requiring high-dose amoxicillin-clavulanate, such as acute otitis media, sinusitis, or pneumonia with suspected resistant pathogens.

Dosing Calculation

Your child weighs 19 kg. The recommended high-dose regimen is 90 mg/kg/day of the amoxicillin component, divided into 2 doses 1.

• Total daily amoxicillin needed: 19 kg × 90 mg/kg = 1,710 mg/day
• Per dose: 1,710 mg ÷ 2 = 855 mg per dose
• Volume needed: If using 125 mg/5 mL suspension, this equals approximately 34 mL per dose

However, this calculation reveals a critical issue: The standard Augmentin 125 mg/5 mL formulation is not appropriate for high-dose therapy in your child.

Correct Formulation Selection

You need a different Augmentin formulation. The evidence strongly supports using:

• Augmentin ES-600 (600 mg amoxicillin/5 mL): Give 7.5 mL twice daily for a 19 kg child 1
• OR Augmentin 400 mg/5 mL suspension: Give approximately 10.5 mL twice daily

The 125 mg/5 mL formulation you have is designed for standard-dose therapy (45 mg/kg/day), not the high-dose regimen recommended for resistant pathogens 2.

Clinical Context Matters

When High-Dose is Required (90 mg/kg/day):

• Acute otitis media with treatment failure or in children <2 years attending daycare 3
• Acute bacterial sinusitis with moderate-to-severe illness 3
• Community-acquired pneumonia with suspected resistant Streptococcus pneumoniae 2
• Recent antibiotic use within past 30 days 3

For these conditions, the 125 mg/5 mL formulation is inadequate.

When Standard-Dose May Be Acceptable (45 mg/kg/day):

• Mild infections in children ≥2 years without recent antibiotic exposure
• β-lactamase producing Haemophilus influenzae infections 2

If using 125 mg/5 mL for standard dosing: Give approximately 17 mL twice daily (provides ~45 mg/kg/day)

Important Caveats

Clavulanate content varies significantly between formulations 1:

• Augmentin 125 mg/5 mL: 31.25 mg clavulanate/5 mL
• Augmentin ES-600: 42.9 mg clavulanate/5 mL
• Augmentin 400 mg/5 mL: 57 mg clavulanate/5 mL

These are NOT interchangeable 1. Using the wrong formulation can result in either inadequate amoxicillin dosing or excessive clavulanate (causing diarrhea).

Practical Recommendation

Contact the prescriber immediately to clarify:

1. The indication for treatment (determines if high-dose is needed)
2. Whether Augmentin 125 mg/5 mL is the intended formulation
3. If high-dose therapy is required, request a prescription for Augmentin ES-600 or the 400 mg/5 mL formulation

Do not attempt to compensate for low concentration by giving large volumes of the 125 mg/5 mL suspension—this provides excessive clavulanate and increases gastrointestinal side effects 4.

Administration Tips

• Give at the start of meals to minimize GI upset and optimize clavulanate absorption 1
• Shake suspension well before each dose 1
• Complete the full 10-day course for most respiratory infections 2, 3
• Watch for diarrhea (occurs in 11-26% of children) and diaper rash 1, 4