Maximum Dosing of Cephalexin for Pediatric UTI
For pediatric patients with urinary tract infections (UTI), the maximum dosage of cephalexin (Keflex) is 100 mg/kg/day divided into four doses, with a maximum daily dose of 4 grams. 1
Standard Dosing Guidelines
- The usual recommended daily dosage for pediatric patients is 25 to 50 mg/kg divided into 4 doses (every 6 hours) 1
- For severe infections, including UTIs, the dosage may be doubled to 50-100 mg/kg/day 1
- In the treatment of otitis media, clinical studies have shown that a higher dosage of 75 to 100 mg/kg/day in 4 divided doses is required, which can be considered the maximum dosing range 1
Weight-Based Dosing Chart
For cephalexin suspension:
| Weight | 125 mg/5 mL | 250 mg/5 mL |
|---|---|---|
| 10 kg (22 lb) | 1/2 to 1 tsp q.i.d. | 1/4 to 1/2 tsp q.i.d. |
| 20 kg (44 lb) | 1 to 2 tsp q.i.d. | 1/2 to 1 tsp q.i.d. |
| 40 kg (88 lb) | 2 to 4 tsp q.i.d. | 1 to 2 tsp q.i.d. |
Note: q.i.d. = four times daily 1
Duration of Therapy
- For uncomplicated UTIs, treatment should typically continue for 7-14 days 1
- For UTIs caused by beta-hemolytic streptococci, therapy should be administered for at least 10 days to prevent complications 1
Special Considerations
- Children may require higher doses per kilogram than adults due to their greater body water turnover 2
- Cephalexin is rapidly cleared from the body by the kidneys, with 70-100% of the dose found in the urine 6-8 hours after administration 2
- Concentrations of 500-1000 μg/ml of urine follow 250 to 500 mg oral doses of cephalexin, which is many times greater than the minimum inhibitory concentration for the usual urinary tract pathogens 2
Dosing in Renal Impairment
- Patients with creatinine clearances less than 30 ml/min require a reduction in cephalexin dosage 2
- The reduction should be proportional to the reduced renal function, which can be established by determination of creatinine clearance or serum creatinine 2
Alternative Dosing Schedules
- For some pediatric UTIs, a shorter course of therapy may be effective. A 3-day course of cephalexin at 25-50 mg/kg/day has shown 90% immediate cure rates in children with lower UTIs 3
- For streptococcal pharyngitis and skin/skin structure infections in patients over 1 year of age, the total daily dose may be divided and administered every 12 hours instead of every 6 hours 1
Clinical Pearls
- If daily doses of cephalexin greater than 4 g are required, parenteral cephalosporins in appropriate doses should be considered 1
- After mixing cephalexin suspension, store in refrigerator where it may be kept for 14 days without significant loss of potency 1
- Cephalexin has good efficacy against common UTI pathogens and achieves high urinary concentrations, making it an appropriate choice for urinary tract infections 2