What are the recommended IV (intravenous) antibiotics for abdominal infections?

Recommended IV Antibiotics for Abdominal Infections

For complicated intra-abdominal infections, ceftazidime-avibactam 2.5 g IV q8h plus metronidazole 500 mg IV q6h is recommended as first-line therapy, with alternatives including imipenem/cilastatin/relebactam or tigecycline-based regimens depending on local resistance patterns. 1

First-Line Treatment Options

For Community-Acquired Intra-Abdominal Infections:

• Piperacillin-tazobactam: 4.5 g IV every 6 hours 2, 3

  • Provides excellent coverage against gram-negative, gram-positive, and anaerobic organisms
  • Consider extended infusion over 3-4 hours for improved pharmacodynamics in serious infections

• Ceftriaxone + Metronidazole: Ceftriaxone 1-2 g IV daily plus Metronidazole 500 mg IV every 8 hours 2

  • Reasonable alternative with similar coverage to piperacillin-tazobactam

• Carbapenems:

  • Ertapenem: 1 g IV every 24 hours 1
  • Meropenem: 1 g IV every 8 hours 4, 5
  • Imipenem/cilastatin: 500 mg IV every 6 hours 1

Treatment for Resistant Organisms

For Carbapenem-Resistant Enterobacterales (CRE):

• Ceftazidime-avibactam: 2.5 g IV q8h plus metronidazole 500 mg IV q6h (weak recommendation, very low quality evidence) 1
• Imipenem-cilastatin-relebactam: 1.25 g IV q6h (weak recommendation, low quality evidence) 1
• Tigecycline: 100 mg IV loading dose, then 50 mg IV q12h (weak recommendation, very low quality evidence) 1
• Eravacycline: 1 mg/kg IV q12h (weak recommendation, very low quality evidence) 1

For Vancomycin-Resistant Enterococci (VRE):

• Linezolid: 600 mg IV q12h (strong recommendation, low quality evidence) 1
• Tigecycline: 100 mg IV loading dose, then 50 mg IV q12h (weak recommendation, very low quality evidence) 1

Treatment Duration

• Standard duration: 5-7 days for uncomplicated infections with adequate source control 1, 2
• Extended duration: 7-14 days for:
  • Immunocompromised patients
  • Inadequate source control
  • Persistent clinical symptoms
  • Bacteremia

Special Considerations

For Severe Infections/Septic Shock:

• Consider combination therapy with broader coverage
• For polymicrobial infections with suspected resistant organisms:
  • Colistin 5 mg CBA/kg IV loading dose, then 2.5 mg CBA (1.5 CrCl + 30) IV q12h + Tigecycline 100 mg IV loading dose, then 50 mg IV q12h 1
  • OR Meropenem 1 g IV q8h by extended infusion 1

For Necrotizing Infections:

• Mixed infection treatment options:
  • Ampicillin-sulbactam: 1.5-3 g every 6-8 h IV
  • Piperacillin-tazobactam: 3.375 g every 6-8 h IV
  • Plus Clindamycin: 600-900 mg/kg every 8 h IV
  • Plus Ciprofloxacin: 400 mg every 12 h IV 1

Dosing Adjustments

Renal Impairment:

• Piperacillin-tazobactam:
  • CrCl 20-40 mL/min: 4.5 g IV every 8 hours
  • CrCl <20 mL/min: 4.5 g IV every 12 hours
  • Hemodialysis: 4.5 g IV every 12 hours, with additional dose after dialysis 2, 3

Pediatric Dosing:

• Piperacillin-tazobactam: 200-300 mg/kg/day of piperacillin component divided every 6-8 hours 3

Common Pitfalls to Avoid

1. Inadequate source control: Surgical intervention or drainage is essential alongside antibiotics 1, 6

2. Delayed or inappropriate therapy: Can lead to increased mortality, need for reoperation, or prolonged hospitalization 1

3. Underdosing: Particularly in critically ill patients with altered pharmacokinetics 2

4. Failure to consider resistant organisms: Especially in healthcare-associated infections or patients with recent antibiotic exposure 1

5. Overlooking C. difficile: Consider in patients with recent antibiotic exposure 2

6. Prolonged therapy: Can lead to resistance development and adverse effects including C. difficile infection 2

7. Failure to de-escalate: Narrow therapy based on culture results when available 6

By following these evidence-based recommendations and avoiding common pitfalls, optimal outcomes can be achieved in the management of intra-abdominal infections.