Cloxacillin Dosing for a 4-Year-Old Child Weighing 15 kg
For a 4-year-old girl weighing 15 kg, administer cloxacillin 50 mg/kg/dose four times daily (QDS), which equals 750 mg per dose or 15 mL of the 250 mg/5 mL suspension four times daily, for a total daily dose of 3000 mg (60 mL/day). 1
Dosing Calculation and Rationale
Standard pediatric dosing for cloxacillin (also known as flucloxacillin) is 50 mg/kg QDS for serious staphylococcal infections including osteomyelitis, mastoiditis, and staphylococcal pneumonia 1
For this 15 kg child:
- 50 mg/kg × 15 kg = 750 mg per dose
- Given four times daily = 3000 mg total daily dose
- Using 250 mg/5 mL suspension: 750 mg ÷ 50 mg/mL = 15 mL per dose
Clinical Context and Duration
Cloxacillin is specifically indicated for methicillin-susceptible Staphylococcus aureus (MSSA) infections 1, 2
Treatment duration varies by indication:
Important Caveats
Bioavailability considerations: Dispersible formulations show better absorption in infants under 6 months compared to older children, while older children achieve higher plasma concentrations with tablets versus liquid formulations 3
Timing with food: There is no significant difference in plasma concentrations whether cloxacillin is given fasting or with meals 3
MRSA coverage: If methicillin-resistant S. aureus is suspected, cloxacillin is ineffective and clindamycin (30-40 mg/kg/day in 3-4 divided doses) should be used instead 4, 5
Combination therapy: For severe staphylococcal infections requiring parenteral therapy, cloxacillin 50 mg/kg QDS should be combined with gentamicin 7.5 mg/kg daily 1
Maximum dose: While pediatric dosing is weight-based, ensure the calculated dose does not exceed typical adult doses (500 mg QDS for mild infections, up to 2 g QDS for severe infections) 1