Cefotaxime (Taxim) Dosing for a 9-Month-Old Infant Weighing 8.6 kg
For a 9-month-old infant weighing 8.6 kg, administer cefotaxime 50 mg/kg every 6–8 hours intravenously or intramuscularly, which equals approximately 430 mg per dose (4.3 mL of a 100 mg/mL solution), given 3–4 times daily depending on infection severity.
Age-Appropriate Dosing Algorithm
Standard Dosing for Infants 1–12 Months
For infants aged 1 month to 12 years with body weight less than 50 kg, the FDA-approved dosing range is 50–180 mg/kg/day divided into 4–6 equal doses, with higher dosages reserved for severe or serious infections including meningitis. 1
For this 8.6 kg infant, the standard dose of 50 mg/kg every 6–8 hours translates to 430 mg per dose (50 mg/kg × 8.6 kg = 430 mg), administered either:
- Every 8 hours (three times daily) = 1,290 mg/day total, OR
- Every 6 hours (four times daily) = 1,720 mg/day total 1
Indication-Specific Considerations
For moderate-to-severe infections (pneumonia, urinary tract infections, soft tissue infections), the ESCMID guideline recommends cefotaxime 75 mg/kg every 6–8 hours for children aged 1 month to 18 years. 2
For bacterial meningitis or life-threatening infections, escalate to 100 mg/kg every 6 hours (maximum 12 grams daily), which would be 860 mg every 6 hours for this infant. 2, 1
For uncomplicated infections, the lower end of 50 mg/kg every 8–12 hours is appropriate. 1
Practical Dosing Recommendation
For this 8.6 kg infant with a presumed moderate infection:
Administer 430 mg (approximately 4.3 mL of 100 mg/mL reconstituted solution) intravenously every 8 hours, providing a total daily dose of 1,290 mg (150 mg/kg/day). 1
If the infection is severe or meningitis is suspected, increase to 645 mg (75 mg/kg) every 6 hours or 860 mg (100 mg/kg) every 6 hours for CNS infections. 2, 1
Evidence Supporting Extended Dosing Intervals
Research demonstrates that 75 mg/kg every 8 hours produces serum concentrations adequate to kill common pediatric pathogens and may improve compliance compared to every-6-hour dosing. 3
Pharmacokinetic studies in infants show that 50 mg/kg every 6 hours maintains therapeutic serum and CSF concentrations with a mean elimination half-life of 0.8 hours and CSF penetration of approximately 10% in meningitis. 4
Population pharmacokinetic modeling confirms that weight, gestational age, and postnatal age significantly impact cefotaxime clearance, supporting weight-based dosing adjustments. 5
Treatment Duration
Continue therapy 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 meningitis, extend treatment to 10–14 days depending on the pathogen and clinical response. 2
Critical Safety Considerations
Do not use cefotaxime in hyperbilirubinemic neonates due to risk of bilirubin encephalopathy from displacement of bilirubin from albumin binding sites. 1
Monitor renal function as cefotaxime is substantially excreted by the kidney; adjust dosing in renal impairment. 1
Administer intravenous doses over 20–30 minutes to minimize infusion-related reactions; intramuscular injection should be deep into a large muscle mass. 1
Common Pitfalls to Avoid
Do not underdose severe infections: Always use the higher end of the dosing range (75–100 mg/kg every 6 hours) for sepsis, meningitis, or documented resistant organisms. 2, 1
Do not extend dosing intervals beyond 8 hours for serious infections in infants, as the short half-life (0.8–1 hour) requires frequent administration to maintain therapeutic concentrations. 4
Do not confuse cefotaxime with ceftriaxone: Unlike ceftriaxone (which can be dosed once daily), cefotaxime requires 3–4 daily doses due to its shorter half-life. 3