A 42-year-old man with a history of gallstones presents with acute onset epigastric pain, nausea, and vomiting. Serum amylase is elevated at 800 U/L. Abdominal ultrasound confirms acute pancreatitis secondary to choledocholithiasis. After initial fluid resuscitation and supportive care, which antibiotic is the drug of choice for prophylaxis in this patient with predicted severe acute pancreatitis (APACHE score 8)?

## Antibiotic Prophylaxis in Severe Acute Pancreatitis **Key Point:** Meropenem (a carbapenem) is the antibiotic of choice for prophylaxis in predicted severe acute pancreatitis because of superior pancreatic tissue penetration and broad-spectrum coverage against gram-negative and gram-positive organisms. ### Rationale for Meropenem **High-Yield:** Carbapenems achieve excellent concentrations in pancreatic tissue and pancreatic necrosis, making them superior to other beta-lactams for this indication. Meropenem is preferred over imipenem due to lower seizure risk. ### Indications for Prophylactic Antibiotics Prophylactic antibiotics are indicated when: - APACHE score ≥ 8 (as in this case) - Ranson score ≥ 3 - CRP > 150 mg/L - CT severity index predicts severe disease - Signs of organ failure **Clinical Pearl:** Prophylactic antibiotics reduce infectious complications and mortality in severe acute pancreatitis. The duration is typically 7–14 days or until clinical improvement. ### Comparison of Antibiotic Options | Antibiotic | Pancreatic Penetration | Spectrum | Use in SAP | |---|---|---|---| | Meropenem | Excellent | Broad (gram +/−) | **First-line** | | Ciprofloxacin | Moderate | Gram-negative | Second-line alternative | | Ceftriaxone | Poor | Gram +/− | Not recommended | | Ampicillin | Poor | Limited | Not recommended | **Warning:** Ceftriaxone and ampicillin have inadequate pancreatic tissue penetration and are not suitable for severe acute pancreatitis prophylaxis, despite being broad-spectrum agents. ### Alternative Regimen If meropenem is contraindicated (e.g., severe allergy), ciprofloxacin + metronidazole is an acceptable alternative, though less effective than carbapenems [cite:Harrison 21e Ch 346].