What antibiotics are used to treat diverticulitis?

Antibiotic Treatment for Diverticulitis

For diverticulitis, first-line antibiotic therapy includes oral amoxicillin-clavulanate or cefalexin with metronidazole for uncomplicated cases, while complicated diverticulitis requires intravenous therapy with ceftriaxone plus metronidazole, piperacillin-tazobactam, or ampicillin/sulbactam. 1

Classification and Antibiotic Selection

Uncomplicated Diverticulitis

• Oral regimens:
  • Amoxicillin-clavulanate
  • Cefalexin with metronidazole
  • For penicillin allergies: Ciprofloxacin plus metronidazole 1, 2

Complicated Diverticulitis

• Intravenous regimens:
  • Ceftriaxone plus metronidazole
  • Piperacillin-tazobactam
  • Ampicillin/sulbactam
  • For severe penicillin allergies: Aztreonam plus metronidazole 1

Treatment Approach Based on Severity

Mild Uncomplicated Diverticulitis

• Recent evidence suggests observation with pain management may be sufficient
• Antibiotics should be reserved for patients with:
  • Persistent fever or chills
  • Increasing leukocytosis
  • Age >80 years
  • Pregnancy
  • Immunocompromised status
  • Chronic medical conditions (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 2

Moderate-Severe Uncomplicated Diverticulitis

• Oral antibiotics for outpatient management
• Duration: Typically 7-10 days 1
• Reassessment at 4-7 days to confirm improvement 1

Complicated Diverticulitis

• Intravenous antibiotics plus:
  • Small abscesses (<4-5 cm): Antibiotics alone
  • Large abscesses (≥4-5 cm): Percutaneous drainage plus antibiotics
  • Peritonitis or perforation: Surgical intervention with antibiotics 1

Outpatient vs. Inpatient Management

Outpatient treatment with oral antibiotics is appropriate for uncomplicated diverticulitis when:

• Patient can tolerate oral intake
• No significant comorbidities
• Adequate family support
• No signs of systemic illness 3

Recent research shows outpatient oral antibiotic therapy is as effective as intravenous antibiotics for uncomplicated diverticulitis, with success rates of approximately 97% 3, 4.

Common Pitfalls and Caveats

1. Misdiagnosis: Clinical suspicion alone is correct in only 40-65% of cases; CT imaging is essential for accurate diagnosis 1

2. Penicillin Allergy Misconception: Many patients who believe they have penicillin allergies do not have true allergies. Consider referral for allergy testing after failure of first-line therapy 1

3. Overtreatment: Not all uncomplicated diverticulitis requires antibiotics. Consider observation with pain management for mild cases without systemic symptoms 2

4. Inadequate Follow-up: Failure to reassess at 4-7 days may miss treatment failures or complications 1

5. Delayed Surgical Consultation: Immediate surgical consultation is necessary for peritonitis or hemodynamic instability 1

6. Atypical Presentation in Elderly: Only 50% of elderly patients present with typical lower quadrant pain; maintain a lower threshold for imaging and treatment 1

By following these evidence-based recommendations, clinicians can effectively manage diverticulitis while minimizing unnecessary antibiotic use and hospitalizations.