Beta-lactam Antibiotic Regimen for Peritonitis
For patients with peritonitis, meropenem 1 g every 6 hours administered by extended or continuous infusion is the recommended beta-lactam antibiotic regimen, especially in critically ill patients or those with septic shock. 1
First-line Beta-lactam Options Based on Patient Status
Non-critically Ill, Immunocompetent Patients with Adequate Source Control
- Piperacillin/tazobactam 4.5 g every 6 hours (or 16 g/2 g by continuous infusion) 1
- Amoxicillin/clavulanate 2 g/0.2 g every 8 hours (for less severe cases) 1
Critically Ill Patients or Immunocompromised Patients
- Piperacillin/tazobactam 4.5 g every 6 hours (or 16 g/2 g by continuous infusion) 1
- Meropenem 1 g every 6 hours by extended infusion or continuous infusion 1
- Doripenem 500 mg every 8 hours by extended infusion or continuous infusion 1
- Imipenem/cilastatin 500 mg every 6 hours by extended infusion 1
Patients with Septic Shock
- Meropenem 1 g every 6 hours by extended infusion or continuous infusion 1
- Doripenem 500 mg every 8 hours by extended infusion or continuous infusion 1
- Imipenem/cilastatin 500 mg every 6 hours by extended infusion 1
Special Considerations
Beta-lactam Allergy
For patients with documented beta-lactam allergy, consider:
- Eravacycline 1 mg/kg every 12 hours 1
- Tigecycline 100 mg loading dose, then 50 mg every 12 hours 1
- Ciprofloxacin 400 mg every 8 hours plus Metronidazole 500 mg every 6 hours 1
Risk for MDR Pathogens or ESBLs
- Imipenem/cilastatin-relebactam 1.25 g every 6 hours by extended infusion 1
- Meropenem/vaborbactam 2 g/2 g every 8 hours by extended infusion 1
- Ceftazidime/avibactam 2.5 g every 8 hours plus Metronidazole 500 mg every 8 hours 1
- Ertapenem 1 g every 24 hours (for community-acquired ESBLs) 1
Administration Considerations
Dosing Optimization
- Higher initial loading doses are recommended for beta-lactams in critically ill patients to account for increased volume of distribution 1
- Extended or continuous infusions of beta-lactams are preferred to maximize time above MIC, particularly for less susceptible pathogens 1
- Concentration gradient between plasma and peritoneal space may require increased doses of meropenem to reach adequate concentrations in peritoneal fluid 1, 2
Duration of Therapy
- 4 days for immunocompetent, non-critically ill patients with adequate source control 1
- Up to 7 days for immunocompromised or critically ill patients with adequate source control 1
- Patients with ongoing signs of infection beyond 7 days warrant diagnostic investigation 1
Caveats and Pitfalls
- Inadequate initial dosing is common in critically ill patients due to increased volume of distribution and augmented renal clearance 1
- Standard dosing regimens often fail to achieve therapeutic concentrations in peritoneal fluid, especially for pathogens with higher MICs 2
- Therapeutic drug monitoring should be considered when available, particularly in critically ill patients 1
- Source control remains essential; antimicrobial therapy alone is insufficient for complicated intra-abdominal infections 1
- Early administration of antibiotics is crucial, especially in patients with septic shock 1