Cephalexin Dosing for 2-Year-Old, 35.8 lbs (16 kg)
For a 2-year-old child weighing 16 kg, administer cephalexin 200-400 mg (12.5-25 mg/kg) every 6 hours (four times daily), or 267-533 mg (16.7-33.3 mg/kg) every 8 hours (three times daily), depending on infection severity and type. 1
Standard Dosing Framework
The FDA-approved pediatric dosing for cephalexin is 25-50 mg/kg/day divided into doses 1. For your 16 kg child, this translates to:
Four Times Daily (QID) Dosing:
- Standard infections: 200 mg every 6 hours (25 mg/kg/day total = 800 mg/day)
- Moderate infections: 300 mg every 6 hours (37.5 mg/kg/day total = 1200 mg/day)
- Severe infections: 400 mg every 6 hours (50 mg/kg/day total = 1600 mg/day)
Three Times Daily (TID) Dosing (Alternative):
Recent evidence supports less frequent dosing for improved adherence 2, 3, 4:
- Standard to moderate infections: 267-400 mg every 8 hours (50-75 mg/kg/day)
- Severe infections or bone/joint infections: Up to 720 mg every 8 hours (45 mg/kg/dose, max 1.5g) 2
Infection-Specific Recommendations
Urinary Tract Infections (UTI):
- Dose: 200-400 mg every 6 hours
- Duration: 7-14 days 5
- Cephalexin achieves excellent urinary concentrations (500-1000 mcg/mL) 6, making it highly effective for UTIs
Skin and Soft Tissue Infections:
- Dose: 200-300 mg every 6 hours OR 267-400 mg every 12 hours for uncomplicated cases 1
- Duration: 7-10 days
- The 12-hour dosing option is FDA-approved specifically for skin infections in children over 1 year 1
Streptococcal Pharyngitis:
- Dose: 200-300 mg every 6 hours OR 267-400 mg every 12 hours 1
- Duration: 10 days minimum for β-hemolytic streptococcal infections 1
Otitis Media:
- Dose: 300-400 mg every 6 hours (75-100 mg/kg/day required) 1
- Duration: 7-10 days
- Higher doses are specifically needed for middle ear infections 1
Bone and Joint Infections:
- Dose: 720 mg every 8 hours (45 mg/kg/dose TID) 2
- This higher TID dosing achieved 99% cure rate in recent studies 2
- Well-tolerated with minimal adverse effects 2, 4, 7
Practical Prescribing
Using 125 mg/5 mL suspension (most common for this age):
- 200 mg = 8 mL (1.6 teaspoons)
- 267 mg = 10.7 mL (approximately 2 teaspoons)
- 300 mg = 12 mL (2.4 teaspoons)
- 400 mg = 16 mL (3.2 teaspoons)
Using 250 mg/5 mL suspension:
- 200 mg = 4 mL (0.8 teaspoon)
- 267 mg = 5.3 mL (approximately 1 teaspoon)
- 300 mg = 6 mL (1.2 teaspoons)
- 400 mg = 8 mL (1.6 teaspoons)
Critical Considerations
Adherence advantage: TID dosing significantly improves compliance compared to QID 2, 3, 4. Studies show equivalent clinical outcomes with TID versus QID dosing for most infections 4, making TID preferable when appropriate.
Timing flexibility: Cephalexin can be given without regard to meals as it's absorbed in the upper intestine, not the stomach 6. This improves practical administration.
Refrigeration: After mixing, store suspension refrigerated and discard after 14 days 1.
Renal adjustment: No dose adjustment needed unless creatinine clearance <30 mL/min 6, which is rare in healthy 2-year-olds.
Common Pitfalls to Avoid
- Don't underdose otitis media: Requires 75-100 mg/kg/day (higher end of dosing range) 1
- Don't use for MRSA: Cephalexin has no activity against methicillin-resistant Staphylococcus aureus 1
- Don't use for atypical pneumonia: No activity against Mycoplasma or Chlamydia
- Don't confuse with cefdinir: Cefdinir has inferior outcomes for UTIs compared to cephalexin 8
For most common pediatric infections in this age group, start with 300 mg every 8 hours (TID) for better adherence, or 200-300 mg every 6 hours (QID) if following traditional dosing. Increase to higher doses for otitis media or severe infections.