Cefotaxime Dosage for a 43-Pound (19.5 kg) Child
For a 19.5 kg child, administer cefotaxime 50 mg/kg per dose every 8 hours IV or IM, which equals approximately 975 mg (round to 1000 mg) per dose, for a total daily dose of 3000 mg divided into three doses. 1
Standard Pediatric Dosing
For children 1 month to 12 years with body weight less than 50 kg: The FDA-approved dosing is 50 to 180 mg/kg/day divided into four to six equal doses, administered IV or IM 1
For moderate to severe infections: Use 50-75 mg/kg per dose every 8 hours, which provides adequate serum concentrations for most common pediatric pathogens 2
Calculation for this patient:
- Weight: 19.5 kg
- Dose: 50 mg/kg × 19.5 kg = 975 mg per dose
- Frequency: Every 8 hours (three times daily)
- Total daily dose: 2925 mg (approximately 3000 mg/day or 150 mg/kg/day)
- This falls well within the FDA-approved range of 50-180 mg/kg/day 1
Dosing Interval Rationale
Every 8-hour dosing is preferred over every 6-hour dosing because cephalosporins exhibit time-dependent killing, and maintaining serum concentrations above the MIC for 40-50% of the dosing interval is sufficient for bacterial eradication 2
The 75 mg/kg every 8 hours regimen produces adequate serum concentrations to effectively kill common pediatric pathogens while reducing administration frequency 2
For uncomplicated infections, the lower end of the dosing range (50 mg/kg every 8 hours) is appropriate 1
Severity-Based Adjustments
For uncomplicated infections: 50 mg/kg per dose every 8-12 hours (1-2 grams total daily dose for adults; proportionally less for children) 1
For moderate to severe infections: 50-75 mg/kg per dose every 8 hours 1, 2
For life-threatening infections or meningitis: Increase to 50 mg/kg per dose every 6-8 hours, with maximum doses up to 2 grams every 4-6 hours in severe cases 1
Route of Administration
Both IV and IM routes are acceptable for cefotaxime administration in children 1
IV route is preferred for hospitalized patients or severe infections 3
IM route can be used for outpatient parenteral therapy or when IV access is difficult 3
Duration of Therapy
Continue treatment for a minimum of 48-72 hours after fever resolution or evidence of bacterial eradication 1
For Group A streptococcal infections, treat for a minimum of 10 days to prevent rheumatic fever or glomerulonephritis 1
For urinary tract infections, 7-14 days is recommended 4
Important Clinical Considerations
Maximum daily dose should not exceed 12 grams regardless of weight or severity 1
Cefotaxime forms an active metabolite (desacetylcefotaxime) that acts synergistically with the parent compound, enhancing antibacterial efficacy 5
No renal dose adjustment is needed in children with normal kidney function, but monitor renal function if treatment is prolonged 1
Cefotaxime has excellent activity against most Enterobacteriaceae, Streptococcus pneumoniae (including penicillin-resistant strains), and Haemophilus influenzae 6
Common Pitfalls to Avoid
Do not use every 12-hour dosing for serious infections - this interval is only appropriate for uncomplicated infections or UTIs 3, 1
Do not rely on cefotaxime alone for Pseudomonas aeruginosa infections - it has only moderate activity (MIC50 19 mcg/mL) and should be combined with an aminoglycoside if pseudomonal coverage is needed 6
Do not use cefotaxime as monotherapy for Bacteroides fragilis infections - 10-20% of strains have MICs exceeding achievable serum concentrations 6
Avoid underdosing in immunocompromised patients - these patients may require higher doses within the approved range 7