Ampicillin-Sulbactam IV Dosing for Burn Patients
For burn patients with normal renal function, administer ampicillin-sulbactam 3g IV every 6 hours (2g ampicillin/1g sulbactam), with dose reduction based on creatinine clearance for those with impaired renal function. 1
Standard Dosing for Burn Patients
The FDA-approved dosing for ampicillin-sulbactam ranges from 1.5g to 3g every 6 hours, with the total sulbactam dose not exceeding 4 grams per day 1. For burn patients at risk of serious infections:
- Standard dose: 3g IV every 6 hours (2g ampicillin/1g sulbactam) 1
- Administration: Slow IV injection over 10-15 minutes, or diluted in 50-100mL compatible diluent as infusion over 15-30 minutes 1
- Maximum sulbactam: 4g per day total 1
Dosing Adjustments for Impaired Renal Function
The ratio of ampicillin to sulbactam remains constant regardless of renal function, so both drugs can be adjusted together 2, 3. Use the following FDA-approved renal dosing schedule 1:
- CrCl ≥30 mL/min: 1.5-3g every 6-8 hours 1
- CrCl 15-29 mL/min: 1.5-3g every 12 hours 1
- CrCl 5-14 mL/min: 1.5-3g every 24 hours 1
Calculating Creatinine Clearance
When only serum creatinine is available 1:
- Males: Weight (kg) × (140 - age) / (72 × serum creatinine)
- Females: 0.85 × male calculation
In elderly patients with low muscle mass, serum cystatin C-based eGFR (eGFRcys-c) provides more accurate renal function assessment than creatinine-based calculations 4. The clearance of ampicillin correlates strongly with eGFRcys-c (r = 0.7374) 4.
Special Considerations for Severe Infections
While standard dosing is appropriate for most burn-related infections, if multidrug-resistant organisms (particularly Acinetobacter baumannii) are suspected or confirmed, consider high-dose sulbactam therapy at 9-12g/day divided into 3-4 doses with 4-hour infusions 5, 6. However, this exceeds FDA-approved maximum sulbactam dosing and should be reserved for documented resistant organisms with MIC ≤4 mg/L 5.
Hemodialysis Patients
For burn patients on hemodialysis 3:
- Dosing interval: Every 24 hours 3
- Timing: Administer dose after hemodialysis session 3
- Rationale: Hemodialysis removes approximately 35% of ampicillin and 45% of sulbactam over 4 hours 3
- Half-life on dialysis: Ampicillin 17.4 hours, sulbactam 13.4 hours (reduced to 2.2-2.3 hours during dialysis) 3
Optimizing Drug Exposure
Extended infusion (4-hour) improves pharmacokinetic/pharmacodynamic target attainment, particularly for pathogens with higher MICs 5, 7. This approach:
- Maintains free drug concentrations above MIC for longer duration 7
- Achieves optimal probability of target attainment against MICs ≤8 mg/L for ampicillin and ≤4 mg/L for sulbactam 7
- Reduces nephrotoxicity risk compared to bolus dosing 5
Monitoring and Safety
Monitor renal function closely during therapy, as both ampicillin and sulbactam clearance correlate directly with creatinine clearance 3, 8, 7. Key monitoring parameters:
- Serum creatinine or cystatin C every 2-3 days 4
- Adjust dosing interval if renal function deteriorates 1
- Ampicillin-sulbactam demonstrates lower nephrotoxicity than colistin or polymyxins, making it safer for patients with borderline renal function 5
Critical Pitfalls to Avoid
- Do not use standard dosing intervals in patients with CrCl <30 mL/min - this leads to drug accumulation and increased toxicity risk 1, 3
- Avoid underdosing in severe infections - standard doses may be insufficient for resistant organisms 5
- Do not administer pre-dialysis - timing doses after hemodialysis prevents excessive drug removal 3
- Prolonged systemic antimicrobial prophylaxis is not recommended for burn patients without documented infection, as meta-analyses show questionable clinical benefit 9
Duration of Therapy
Treatment duration should be 7-10 days for most serious infections, with extension to 14 days for severe presentations or slow clinical response 5. The FDA label notes that IV therapy should not routinely exceed 14 days 1.