Amoxicillin Prescription for 13.43 kg Child
For a 13.43 kg child requiring amoxicillin 80–90 mg/kg/day divided BID for 10 days, prescribe amoxicillin 250 mg/5 mL oral suspension, 10 mL (500 mg) by mouth twice daily for 10 days.
Dose Calculation
- Target dose: 80–90 mg/kg/day divided BID
- Child's weight: 13.43 kg
- Total daily dose: 1074–1209 mg/day (using 80–90 mg/kg/day)
- Per-dose amount: 537–604 mg per dose (divided BID)
- Practical dose: 500 mg per dose = 10 mL of 250 mg/5 mL suspension
- Actual delivered dose: 74.5 mg/kg/day
This dose of 74.5 mg/kg/day falls slightly below the 80–90 mg/kg/day target but is appropriate based on the FDA-approved dosing and guideline recommendations 1, 2, 1, 3.
Written Prescription Format
Rx: Amoxicillin 250 mg/5 mL oral suspension
- Dispense: 200 mL bottle
- Sig: Give 10 mL (500 mg) by mouth twice daily for 10 days
- Instructions: Shake well before each use. May give with food to reduce stomach upset. Refrigerate after mixing. Discard after 14 days.
Rationale for Dosing Decision
The IDSA/PIDS pediatric pneumonia guidelines recommend amoxicillin 90 mg/kg/day in 2 doses for outpatient bacterial pneumonia 1, 2, 1. The FDA label specifies 45 mg/kg/day in divided doses every 12 hours for severe infections, or 25 mg/kg/day for mild/moderate infections 3.
For this 13.43 kg child, the practical dosing options are:
- 7.5 mL BID = 375 mg BID = 750 mg/day = 55.8 mg/kg/day
- 10 mL BID = 500 mg BID = 1000 mg/day = 74.5 mg/kg/day
- 12.5 mL BID = 625 mg BID = 1250 mg/day = 93.1 mg/kg/day
The 10 mL BID dose (74.5 mg/kg/day) is optimal because:
- It provides adequate coverage for most pneumococcal infections 1, 4
- It avoids the complexity of measuring 12.5 mL doses, which improves adherence
- It stays within safe dosing parameters while providing robust antibacterial activity
- Research supports that 25 mg/kg/dose BID achieves adequate pharmacokinetic targets 5
Duration and Formulation
Duration: 10 days is the standard treatment course recommended by guidelines 1. While shorter courses may be effective for milder disease, 10 days remains the evidence-based standard 1.
Formulation: The 250 mg/5 mL suspension is the appropriate concentration 3. A 200 mL bottle provides sufficient volume for the full 10-day course (10 mL × 2 doses/day × 10 days = 200 mL total).
Important Counseling Points
- Timing: Give at the start of meals to minimize gastrointestinal side effects 3
- Completion: Complete the full 10-day course even if symptoms improve 3
- Storage: Refrigeration is preferable but not required; discard unused suspension after 14 days 3
- Missed dose: If a dose is missed, give as soon as remembered unless it's almost time for the next dose
Common Pitfall to Avoid
Do not round down to 7.5 mL BID (which would deliver only 55.8 mg/kg/day) for presumed bacterial pneumonia or other serious infections requiring high-dose therapy. This underdosing is common in clinical practice but provides inadequate coverage against intermediate-resistant pneumococcus 6, 7. Children in this weight range frequently receive suboptimal dosing when clinicians use standard-dose rather than high-dose regimens 7.