What is the appropriate dosage of ampicillin (Ampicillin)-sulbactam (Sulbactam) for a 40-kilogram patient?

Ampicillin-Sulbactam Dosing for a 40 kg Patient

For a 40 kg patient, administer ampicillin-sulbactam 12 g per 24 hours IV divided into 4 equally divided doses (3 g every 6 hours), which is the adult dosing regimen. 1

Weight-Based Dosing Threshold

• Pediatric patients weighing 40 kg or more should be dosed according to adult recommendations, with a maximum total sulbactam dose not exceeding 4 grams per day 1
• The standard pediatric dose of 300 mg/kg/day would equal 12 g/day for a 40 kg patient, which aligns exactly with the adult maximum dose 2, 1

Standard Adult Dosing Regimen

• The recommended adult dosage ranges from 1.5 g to 3 g every 6 hours (representing 1 g ampicillin/0.5 g sulbactam to 2 g ampicillin/1 g sulbactam per dose) 1
• For most infections, 3 g every 6 hours (12 g/24 hours total) is appropriate, providing 8 g ampicillin and 4 g sulbactam daily 2, 1
• The total sulbactam dose should not exceed 4 grams per day 1

Administration Guidelines

• Administer by slow IV injection over at least 10-15 minutes, or dilute in 50-100 mL of compatible diluent and infuse over 15-30 minutes 1
• For severe infections or resistant organisms, consider 4-hour extended infusions to optimize pharmacokinetic/pharmacodynamic properties 3

Infection-Specific Dosing

For Endocarditis or Culture-Negative Endocarditis

• 12 g/24 hours IV in 4 equally divided doses (3 g every 6 hours) for 4-6 weeks, typically combined with gentamicin 2, 4

For Severe Multidrug-Resistant Infections

• High-dose sulbactam therapy at 9-12 g/day may be required for organisms with MIC ≤4 mg/L, administered as 3-4 g every 8 hours with 4-hour infusions 3
• This represents the sulbactam component alone; when using ampicillin-sulbactam (2:1 ratio), this would require higher total daily doses

Renal Function Considerations

• For creatinine clearance ≥30 mL/min/1.73m²: Standard dosing of 1.5-3 g every 6-8 hours 1
• For creatinine clearance 15-29 mL/min/1.73m²: 1.5-3 g every 12 hours 1
• For creatinine clearance 5-14 mL/min/1.73m²: 1.5-3 g every 24 hours 1

Common Pitfalls to Avoid

• Do not underdose when treating resistant organisms - doses below 9 g/day of sulbactam may be insufficient for severe infections caused by multidrug-resistant pathogens 3
• Do not exceed 4 grams per day of sulbactam in patients with normal renal function 1
• Do not use pediatric weight-based dosing (300 mg/kg/day) in patients ≥40 kg as this would exceed the maximum safe sulbactam dose 1
• Adjust dosing frequency based on renal function rather than maintaining standard intervals, as both ampicillin and sulbactam are primarily renally eliminated 1, 5

Duration of Therapy

• Typical course is 7-14 days for most infections, though IV therapy should not routinely exceed 14 days 1
• For endocarditis or deep-seated infections, 4-6 weeks may be necessary 2, 4
• Consider transitioning to oral antimicrobials following initial IV therapy when clinically appropriate 1