Cephalexin Dosing for UTI in a 10kg, 22-Month-Old Child
For a 10kg, 22-month-old child with a UTI, administer cephalexin 50-100 mg/kg/day divided into 4 doses (125-250 mg every 6 hours) for 7-14 days. 1
Specific Dosing Calculation
For this 10kg child:
- Standard dose range: 500-1000 mg total daily dose
- Practical dosing: 125-250 mg every 6 hours (four times daily)
- Using suspension: 1-2 teaspoons of 125 mg/5mL suspension every 6 hours, OR 0.5-1 teaspoon of 250 mg/5mL suspension every 6 hours 2
Route of Administration
Oral administration is appropriate for well-appearing children who can tolerate oral intake. 1
- Parenteral therapy (ceftriaxone 50 mg/kg/dose every 24 hours) should be reserved for children who appear toxic, cannot retain oral medications, or when compliance is uncertain 1
- At 22 months of age, this child falls within the 2-24 month guideline range where oral therapy is equally efficacious to parenteral therapy 1
Duration of Therapy
Treat for 7-14 days total. 1
- The American Academy of Pediatrics guidelines specify this range for febrile UTIs in children 2-24 months old 1
- Courses shorter than 7 days have been shown to be inferior 1
- If starting with parenteral therapy, switch to oral once the child shows clinical improvement (typically 24-48 hours) and can retain oral medications 1
Important Clinical Considerations
Local Resistance Patterns
- Check local antibiogram data before prescribing, as there is substantial geographic variability in E. coli resistance to cephalexin 1
- Adjust therapy based on culture and sensitivity results once available 1
When NOT to Use Cephalexin
- Do not use cephalexin if the child appears toxic or septic - use parenteral ceftriaxone instead 1
- Cephalexin should not be used if local resistance rates to first-generation cephalosporins are high 1
- Avoid if the child cannot tolerate oral medications due to vomiting 1
Alternative Oral Options
If cephalexin is not appropriate based on local resistance patterns, consider: 1
- Amoxicillin-clavulanate 20-40 mg/kg/day in 3 doses
- Cefixime 8 mg/kg/day in 1 dose
- Trimethoprim-sulfamethoxazole (if local susceptibility permits)
Common Pitfall
Never use nitrofurantoin for febrile UTIs in young children, as it does not achieve adequate serum concentrations to treat pyelonephritis or urosepsis, even though it concentrates well in urine 1