What is the recommended dosage of cloxacillin (antibiotic) for pediatric patients?

Cloxacillin Dosing for Pediatric Patients

Standard Dosing Recommendations

For pediatric patients with staphylococcal infections, cloxacillin should be dosed at 50-100 mg/kg/day divided into 4 doses (every 6 hours), with higher doses reserved for severe infections such as endocarditis, osteomyelitis, or septic arthritis. 1

Age-Based Dosing Framework

Neonates:

• For gestational age <30 weeks with postnatal age <14 days: Limited data available for cloxacillin specifically; consider alternative anti-staphylococcal agents with established neonatal dosing 1
• For term neonates (≥37 weeks): 25-50 mg/kg/dose IV every 6 hours 1

Infants and Children (>1 month):

• Mild to moderate infections: 50 mg/kg/day divided every 6 hours (12.5 mg/kg/dose) 1
• Severe infections (endocarditis, osteomyelitis, septic arthritis): 100-200 mg/kg/day divided every 6 hours (25-50 mg/kg/dose) 1
• Maximum daily dose: 4000 mg/day (4 g/day), regardless of weight 1

Indication-Specific Dosing

Staphylococcal Endocarditis:

• 200 mg/kg/day divided every 6 hours (50 mg/kg/dose every 6 hours) for 4-6 weeks 1
• This higher dose ensures adequate time above MIC (T>MIC) for optimal bactericidal activity 2

Osteomyelitis and Septic Arthritis:

• 150-200 mg/kg/day divided every 6 hours for 4-6 weeks 1

Skin and Soft Tissue Infections:

• 50-100 mg/kg/day divided every 6 hours for 7-14 days 1

Severe Sepsis with Suspected Staphylococcal Infection:

• When staphylococcal infection is suspected in severe sepsis, add flucloxacillin (cloxacillin equivalent) 50 mg/kg every 6 hours 3

Critical Dosing Considerations

Pharmacokinetic Principles:

• Cloxacillin is a time-dependent antibiotic requiring T>MIC for at least 40-50% of the dosing interval for optimal bactericidal effect 2
• Four times daily dosing (every 6 hours) is essential to maintain adequate drug levels 2

Renal Impairment:

• Major pitfall: Unlike many antibiotics, cloxacillin requires significant dose reduction in renal failure 4
• For creatinine clearance <10 mL/min: Reduce dose by 50% and monitor drug levels if available 4
• Patients on hemodialysis are at particularly high risk for overdosing and neurological side effects 4

Common Pitfalls and How to Avoid Them

Weight-Based Dosing Errors:

• Do not cap doses at "adult maximum" for children weighing >20 kg who still require weight-based dosing 5, 6
• Continue weight-based dosing up to the absolute maximum of 4000 mg/day 1

Underdosing in Severe Infections:

• For endocarditis and osteomyelitis, use the higher end of the dosing range (200 mg/kg/day) to ensure adequate tissue penetration 1, 2
• Inadequate dosing leads to treatment failure in deep-seated staphylococcal infections 2

Renal Function Monitoring:

• Always assess renal function before initiating therapy and monitor during treatment 4
• Neurological side effects (persistent coma, delirium) occur in 17.7% of overdosed patients, particularly those with renal impairment 4

Administration Considerations

Route of Administration:

• Intravenous administration is preferred for severe infections 1, 2
• Oral cloxacillin can be used for mild infections or step-down therapy after clinical improvement 1

Infusion Considerations:

• For severe infections, consider continuous or extended infusion to optimize T>MIC 2
• Standard intermittent dosing every 6 hours is acceptable for most pediatric infections 1