What is the appropriate amoxicillin suspension dose for a 19‑lb (≈8.6‑kg) child?

Amoxicillin Dosing for a 19-Pound (8.6 kg) Child

For a 19-pound (8.6 kg) child, administer 3.9 mL of amoxicillin 250 mg/5 mL suspension twice daily for standard-dose indications, or 7.7 mL twice daily for high-dose indications.

Weight-Based Dose Calculation

Standard-Dose Regimen (45 mg/kg/day)

• For uncomplicated respiratory tract infections in children ≥3 months without risk factors, the recommended dose is 45 mg/kg/day divided into 2 doses (22.5 mg/kg per dose). 1
• For an 8.6 kg child: 8.6 kg × 22.5 mg/kg = 193.5 mg per dose, administered twice daily. 1
• Using 250 mg/5 mL suspension: (193.5 mg ÷ 250 mg) × 5 mL = 3.9 mL per dose, twice daily. 2

High-Dose Regimen (90 mg/kg/day)

• For severe infections, community-acquired pneumonia, or when any of the following risk factors are present—age <2 years, daycare attendance, recent antibiotic use (past 30 days), or residence in areas with >10% penicillin-resistant S. pneumoniae—use 90 mg/kg/day divided into 2 doses (45 mg/kg per dose). 1, 3
• For an 8.6 kg child: 8.6 kg × 45 mg/kg = 387 mg per dose, administered twice daily. 1
• Using 250 mg/5 mL suspension: (387 mg ÷ 250 mg) × 5 mL = 7.7 mL per dose, twice daily. 2

Indication-Specific Dosing Algorithm

When to Use Standard Dose (45 mg/kg/day = 3.9 mL twice daily)

• Mild-to-moderate respiratory tract infections in children ≥2 years without recent antibiotic exposure. 1
• Uncomplicated skin infections or genitourinary infections. 1
• Group A streptococcal pharyngitis: 50–75 mg/kg/day (4.3–6.5 mL twice daily for this child). 1

When to Use High Dose (90 mg/kg/day = 7.7 mL twice daily)

• Any child <2 years old (this 8.6 kg child is likely <2 years based on weight). 1
• Community-acquired pneumonia (presumed bacterial). 1, 3
• Daycare attendance. 1
• Antibiotic use within the past 30 days. 1
• Moderate-to-severe illness. 1
• Geographic area with >10% penicillin-resistant S. pneumoniae. 1

Because a 19-pound child is almost certainly younger than 2 years, the high-dose regimen (7.7 mL twice daily) should be used for most bacterial infections unless specifically treating uncomplicated Group A strep pharyngitis. 1

Treatment Duration and Monitoring

• Continue therapy for 10 days for most respiratory infections and pneumonia. 1, 3
• For Group A streptococcal infections, complete a full 10-day course to prevent acute rheumatic fever, even if symptoms resolve earlier. 1, 2
• Extend treatment for at least 48–72 hours after complete symptom resolution. 1, 2
• Clinical improvement should be evident within 48–72 hours; if no improvement occurs, reevaluate for treatment failure, resistant organisms, or atypical pathogens. 1, 3

Administration Instructions

• Administer at the start of a meal to minimize gastrointestinal intolerance. 2
• Shake the suspension vigorously before each dose. 2
• Place the dose directly on the child's tongue or mix with formula, milk, fruit juice, or water; administer immediately after mixing. 2
• Store reconstituted suspension in the refrigerator (preferred but not required); discard any unused portion after 14 days. 2

Critical Dosing Pitfalls to Avoid

• Do not underdose based on outdated guidelines; current resistance patterns require 45–90 mg/kg/day, not the older 40 mg/kg/day recommendations. 1
• Do not use plain amoxicillin if β-lactamase-producing organisms (H. influenzae, M. catarrhalis) are suspected; switch to amoxicillin-clavulanate 90 mg/kg/day of the amoxicillin component. 1
• Do not discontinue early even if fever resolves; incomplete courses increase relapse risk and do not prevent rheumatic fever. 1, 2
• For children <3 months (12 weeks), the maximum dose is 30 mg/kg/day divided every 12 hours due to immature renal function; do not use standard pediatric dosing. 2

Maximum Dose Limits

• The maximum single dose is 2,000 mg per administration, regardless of weight. 1
• The maximum daily dose is 4,000 mg (4 g) per day. 1, 3
• For this 8.6 kg child, calculated doses (193.5 mg or 387 mg per dose) are well below these limits. 1

When to Escalate Therapy

• If no improvement after 48–72 hours, consider adding a macrolide (azithromycin 10 mg/kg day 1, then 5 mg/kg days 2–5) for atypical pathogens. 1, 3
• Switch to amoxicillin-clavulanate if β-lactamase producers are documented or strongly suspected. 1
• Hospitalize if respiratory distress, inability to tolerate oral intake, or no improvement after 5 days of appropriate therapy. 1