Unasyn Dosing for 6-Year-Old, 24.7 kg Child
For a 6-year-old child weighing 24.7 kg, administer Unasyn (ampicillin-sulbactam) at 1,235 mg every 6 hours intravenously, which provides 300 mg/kg/day (200 mg/kg/day ampicillin + 100 mg/kg/day sulbactam).
Dosing Calculation
The FDA-approved pediatric dosing for Unasyn is 300 mg/kg/day divided every 6 hours for children ≥1 year of age 1. This total daily dose represents the combined ampicillin and sulbactam content in a 2:1 ratio (200 mg/kg/day ampicillin + 100 mg/kg/day sulbactam).
For this 24.7 kg child:
- Total daily dose: 300 mg/kg/day × 24.7 kg = 7,410 mg/day
- Divided every 6 hours: 7,410 mg ÷ 4 = 1,852.5 mg per dose
- This breaks down to approximately 1,235 mg ampicillin + 617.5 mg sulbactam per dose
Practical dosing: Round to 1.85 g (1,850 mg) per dose every 6 hours, or use the nearest available vial size.
Administration Details
- Route: Intravenous infusion over 15-30 minutes 1
- Frequency: Every 6 hours (four times daily)
- Maximum duration: Should not routinely exceed 14 days of IV therapy 1
- Sulbactam maximum: Total sulbactam should not exceed 4 grams per day (this child receives 2.47 g/day, well within limits) 1
Clinical Context and Supporting Evidence
The 300 mg/kg/day dosing is well-established in pediatric literature. Pharmacokinetic studies demonstrate that this regimen achieves therapeutic concentrations comparable to adults, with mean peak concentrations of 177-200 mcg/mL for ampicillin and 82-102 mcg/mL for sulbactam 2. The combination maintains a half-life of approximately 0.77 hours for ampicillin and 0.81 hours for sulbactam in pediatric patients 2.
Important considerations:
- This dosing assumes normal renal function. If creatinine clearance is <30 mL/min/1.73m², adjust frequency to every 12 or 24 hours based on severity of impairment 1
- Clinical trials in pediatric skin/soft tissue infections showed 78% cure rates with this regimen, with excellent safety profile 3
- The 98.7% cure rate was demonstrated across various pediatric infections using 200 mg ampicillin + 100 mg sulbactam per kg/day 4
Transition to Oral Therapy
Most children in clinical trials received oral antimicrobials following initial IV Unasyn treatment 1. Consider step-down therapy once the child shows clinical improvement (typically 24-48 hours), is afebrile, and can tolerate oral intake.
Common pitfall: Do not use the adult weight-based dosing (1.5-3 g every 6 hours) for pediatric patients, as this significantly underdoses children. The pediatric formulation requires the full 300 mg/kg/day calculation 1.