Cefalexin Dosing for a 13.6 kg, 2-Year-Old Child
Give 3.5 mL of cefalexin suspension (125mg/5mL) four times daily (every 6 hours) for 7 days.
Dosage Calculation
- The FDA-approved pediatric dosage for cefalexin is 25-50 mg/kg/day in divided doses 1
- For this 13.6 kg child, the standard dosing range is:
- Minimum: 25 mg/kg/day = 340 mg/day
- Maximum: 50 mg/kg/day = 680 mg/day
- For most infections, use 25 mg/kg/day divided into 4 doses = approximately 85 mg per dose 1
- With the 125mg/5mL suspension, this equals 3.5 mL four times daily (providing 87.5 mg per dose, or 350 mg/day total) 1
Dosing Schedule
- Administer every 6 hours (four times daily: e.g., 6 AM, 12 PM, 6 PM, 12 AM) to maintain therapeutic drug levels 1
- The FDA label specifically recommends q.i.d. (four times daily) dosing for standard infections in pediatric patients 1
- According to the dosing table for a 10 kg child using 125mg/5mL suspension, the range is 1/2 to 1 teaspoon (2.5-5 mL) four times daily; at 13.6 kg, 3.5 mL falls appropriately within this range 1
When to Use Higher Doses
- For severe infections or otitis media, increase to 75-100 mg/kg/day in 4 divided doses 1
- This would be 6-7 mL four times daily for this child (providing approximately 375-437.5 mg per dose) 1
- Higher doses may be needed for less susceptible organisms 1
Administration Instructions
- May be given with or without food, though administration with meals may improve gastrointestinal tolerability 2
- Shake the suspension well before each dose 1
- Store in refrigerator after mixing; discard after 14 days 1
- Use an appropriate measuring device (oral syringe) for accurate dosing 3
Duration and Monitoring
- Complete the full 7-day course even if symptoms improve earlier 2
- For streptococcal infections specifically, continue for at least 10 days 1
- Expect clinical improvement within 48-72 hours; if no improvement occurs, consider alternative diagnoses or resistant organisms 4
Important Caveats
- Cefalexin is not effective against Haemophilus influenzae, with failure rates of 50% in H. influenzae otitis media 5
- It is also not suitable for shigellosis due to inadequate tissue concentrations despite in vitro susceptibility 6
- The drug achieves excellent urinary concentrations (500-1000 mcg/mL) but does not penetrate into CSF or aqueous humor 7
- Adverse effects are generally mild, with gastrointestinal upset being most common; discontinuation is rarely required 5, 8