What dose of amoxicillin 250 mg/5 mL suspension should a 6‑year‑old child weighing 53 lb (≈24 kg) take every 12 hours for a 10‑day course, and how many milliliters total are required?

Amoxicillin Dosing for a 6-Year-Old, 53 lb (24 kg) Child

For this 24 kg child taking amoxicillin 250 mg/5 mL suspension every 12 hours for 10 days, prescribe 10 mL (500 mg) per dose, requiring a total of 200 mL for the complete course.

Dose Calculation

Weight-Based Dosing

• The child weighs 53 lbs = 24 kg 1
• For mild to moderate infections (ear/nose/throat, skin, genitourinary), the FDA-approved dosing is 25 mg/kg/day divided every 12 hours 1
• For severe infections or lower respiratory tract infections, dosing is 45 mg/kg/day divided every 12 hours 1

Standard Dosing Approach

• For mild/moderate infections: 25 mg/kg/day ÷ 2 doses = 12.5 mg/kg/dose = 300 mg per dose 1
• For severe infections or pneumonia: 45 mg/kg/day ÷ 2 doses = 22.5 mg/kg/dose = 540 mg per dose 1

Practical Prescription Using 250 mg/5 mL Suspension

For mild/moderate infections:

• 300 mg per dose = 6 mL per dose (provides 300 mg)
• Total volume needed: 6 mL × 2 doses/day × 10 days = 120 mL

For severe infections or suspected pneumococcal disease:

• 500 mg per dose = 10 mL per dose (provides 500 mg, approximately 21 mg/kg/dose)
• Total volume needed: 10 mL × 2 doses/day × 10 days = 200 mL

Clinical Context Determines Dosing

When to Use Standard Dose (6 mL per dose)

• Uncomplicated acute otitis media 1
• Simple skin and soft tissue infections 1
• Uncomplicated urinary tract infections 1

When to Use High Dose (10 mL per dose)

• Community-acquired pneumonia: High-dose amoxicillin (80-90 mg/kg/day) is preferred for pneumococcal coverage 2
• Acute otitis media with treatment failure or in regions with high pneumococcal resistance 3
• Any suspected pneumococcal infection given increasing intermediate penicillin resistance 3, 4

Bottle Size Recommendation

For Standard Dose (Mild Infections)

• Request 150 mL bottle (provides 120 mL needed plus buffer) 1

For High Dose (Severe Infections/Pneumonia)

• Request 200 mL bottle or two 100 mL bottles 1

Important Prescribing Details

Administration Instructions

• Take at the start of meals to minimize gastrointestinal intolerance 1
• Shake suspension well before each use 1
• Can be mixed with formula, milk, fruit juice, water, or cold drinks if needed, but must be taken immediately after mixing 1

Storage and Stability

• Refrigeration is preferable but not required 1
• Discard any unused suspension after 14 days of reconstitution 1
• Keep bottle tightly closed 1

Duration Considerations

• 10-day duration is appropriate for most bacterial infections to ensure adequate bacterial eradication 1
• For Group A Streptococcal infections, at least 10 days of treatment is mandatory to prevent acute rheumatic fever 1
• Recent evidence suggests shorter courses (3-5 days) may be adequate for uncomplicated pneumonia with early clinical improvement, but 10 days remains standard practice 5, 6

Common Pitfalls to Avoid

Underdosing Larger Children

• Children over 20 kg frequently receive subtherapeutic doses when clinicians cap at "adult maximum doses" 4
• Do not artificially limit to 500 mg per dose if weight-based dosing indicates higher amounts are needed 4
• This 24 kg child can safely receive 500-540 mg per dose for severe infections 1, 4

Inadequate Pneumococcal Coverage

• Standard-dose amoxicillin (25 mg/kg/day) achieves only 4% probability of target attainment against CLSI breakpoints for resistant pneumococci 3
• High-dose amoxicillin (80-90 mg/kg/day) achieves >73% probability of target attainment and is essential for pneumococcal infections 3

Incorrect Suspension Concentration

• Verify you are prescribing 250 mg/5 mL concentration (not 125 mg/5 mL or 400 mg/5 mL formulations) 1
• Double-check volume calculations to avoid 10-fold dosing errors