What is the typical dosage of amoxicillin (amoxicillin) for a 9-year-old child?

Amoxicillin Dosage for a 9-Year-Old Child

For a 9-year-old child, amoxicillin dosing is weight-based rather than age-based, with the standard dose being 45 mg/kg/day divided into 2 doses (every 12 hours) for mild to moderate infections, or 90 mg/kg/day divided into 2 doses for severe infections or areas with high pneumococcal resistance, with a maximum daily dose of 4000 mg. 1, 2

Weight-Based Dosing Approach

The critical first step is determining the child's weight, as all pediatric amoxicillin dosing is weight-based rather than age-based 1:

• For children weighing less than 40 kg: Use 25 mg/kg/day divided every 12 hours (or 20 mg/kg/day divided every 8 hours) for mild to moderate infections 2
• For children weighing 40 kg or more: Use adult dosing of 500 mg every 12 hours (or 250 mg every 8 hours) for mild to moderate infections 2, 3

Indication-Specific Dosing

Respiratory Tract Infections (Including Pneumonia)

• Mild to moderate infections: 45 mg/kg/day divided into 2 doses (every 12 hours) 1, 2
• Severe infections or high pneumococcal resistance areas: 90 mg/kg/day divided into 2 doses (every 12 hours) 1, 2
• Treatment duration: 7-10 days for most respiratory infections; pneumonia specifically requires 10 days 1, 2

Group A Streptococcal Infections (Strep Throat, Scarlet Fever)

• Dose: 50-75 mg/kg/day divided into 2 doses for 10 days, not exceeding 1000 mg per dose 1, 2
• Critical consideration: The full 10-day course is mandatory to prevent rheumatic fever, even if symptoms resolve earlier 2, 3
• Patients become non-contagious after 24 hours of therapy 2

Ear/Nose/Throat and Skin Infections

• Mild to moderate: 25 mg/kg/day divided every 12 hours 3
• Severe: 45 mg/kg/day divided every 12 hours 3

Practical Dosing Examples

For a typical 9-year-old weighing approximately 30 kg:

• Mild to moderate infection: 45 mg/kg/day = 1350 mg/day ÷ 2 doses = 675 mg twice daily 1
• Severe infection: 90 mg/kg/day = 2700 mg/day ÷ 2 doses = 1350 mg twice daily 1

Critical Administration Details

Every prescription should clearly specify: 2

• Total daily dose in mg/kg/day
• Number of divided doses per day
• Duration of therapy
• Indication for prescription
• Child's weight

Dosing Frequency: Why Twice Daily is Preferred

Twice-daily dosing (every 12 hours) improves adherence compared to three-times-daily regimens and is equally effective 2, 4. Research demonstrates that once or twice daily amoxicillin produces comparable clinical cure rates to three times daily dosing 4, making the every-12-hour schedule the preferred approach for better compliance 2.

Monitoring and Follow-Up

• Expected improvement: Children should demonstrate clinical improvement within 48-72 hours of starting treatment 1, 2
• If no improvement by 72 hours: Reassess the diagnosis and consider alternative antibiotics 2
• Complete the full course: Even if symptoms improve before completion 1, 2

Common Pitfalls to Avoid

• Underdosing in high-resistance areas: The traditional 40 mg/kg/day dosing is inadequate for resistant Streptococcus pneumoniae; use 90 mg/kg/day for severe infections or high-resistance areas 1, 5
• Premature discontinuation: Particularly critical for streptococcal infections where the full 10-day course prevents rheumatic fever 2, 3
• Age-based instead of weight-based dosing: Always calculate based on actual body weight 1, 2
• Forgetting maximum daily dose: Never exceed 4000 mg (4 g) per day regardless of calculated weight-based dose 1, 2

Administration Tips

• Administer at the start of a meal to minimize gastrointestinal intolerance 3
• Shake oral suspension well before each use 3
• Refrigeration of suspension is preferable but not required; discard unused portion after 14 days 3

Common Adverse Effects

• Most common: Gastrointestinal disturbances including diarrhea, nausea, and vomiting 1, 2
• Also possible: Rash, urticaria, and hypersensitivity reactions 1, 2