Weight-Based Dosing of Cephalexin for a 30-Pound Child
The recommended weight-based dose of cephalexin for a child weighing 30 pounds (approximately 13.6 kg) is 25-50 mg/kg/day divided into 4 doses, which equals approximately 340-680 mg total daily dose, or 85-170 mg per dose given four times daily. 1
Dosage Calculation
To calculate the appropriate dose:
- Child's weight: 30 pounds = 13.6 kg
- According to the FDA label, the usual recommended daily dosage for pediatric patients is 25-50 mg/kg divided into doses 1
- At 25 mg/kg/day: 13.6 kg × 25 mg/kg = 340 mg/day
- At 50 mg/kg/day: 13.6 kg × 50 mg/kg = 680 mg/day
Standard Dosing Schedule
- Four times daily (q6h): 85-170 mg per dose
- Using the commercially available suspension:
- With 125 mg/5 mL suspension: 3.4-6.8 mL (approximately ¾-1⅓ teaspoons) per dose
- With 250 mg/5 mL suspension: 1.7-3.4 mL (approximately ⅓-⅔ teaspoons) per dose
Clinical Considerations
Infection Type
The specific dose within the 25-50 mg/kg/day range depends on the type and severity of infection:
- For mild to moderate infections: 25-30 mg/kg/day
- For more severe infections: The dosage may be doubled up to 50 mg/kg/day 1
- For otitis media: Higher dosages of 75-100 mg/kg/day in 4 divided doses have been shown to be required 1
- For streptococcal pharyngitis: Treatment should continue for at least 10 days 1
Alternative Dosing Regimens
While the FDA-approved dosing is four times daily, recent research has explored less frequent dosing to improve adherence:
- A 2020 study suggests that for methicillin-susceptible Staphylococcus aureus infections, three-times-daily dosing at 15-25 mg/kg per dose may be effective 2
- However, for clinical practice, the FDA-approved four-times-daily regimen remains the standard recommendation 1
Important Considerations
Administration
- Cephalexin can be administered with or without food
- The suspension should be refrigerated after reconstitution and can be kept for 14 days without significant loss of potency 1
Duration of Treatment
- For most infections: 7-14 days
- For streptococcal infections: Minimum of 10 days 1
Monitoring
- Monitor for signs of allergic reactions, especially in patients with a history of penicillin allergy
- Watch for gastrointestinal side effects, which are generally mild but may include diarrhea
Advantages of Cephalexin
- Cephalexin is rapidly absorbed from the upper intestine and achieves good tissue distribution 3
- It is generally well-tolerated with a low incidence of side effects 3
- It provides effective coverage against common pathogens involved in pediatric infections 3
Remember that cephalexin does not require dosage adjustment for children with normal renal function, but dose reduction may be necessary for those with significant renal impairment (creatinine clearance <30 mL/min) 3.