Antibiotics for Diverticulitis

Based on "Diagnosis and Management of Acute Diverticulitis"
written by Thad Wilkins, MD; Katherine Embry, MD; Ruth George, MD

What is a Diverticulitis?

Diverticulitis is an inflammation of one or more diverticula, which are small pouches, resulted from herniations or protrusions of the intestinal mucosa and submucosa.

Diverticulosis (also known as diverticular disease), is the condition of having diverticula (pouch) in the colon.

Signs & Symptoms

Signs and symptoms of diverticulitis depend on the location of the affected diverticulum, degree and extent of the inflammation, and complications. The disease can affect any part of the colon, but the vast majority of diverticula develop in the sigmoid colon.

The most common symptoms and complaints are:

  • Left lower quadrant pain (develops in 70% of patients)
  • Nausea and vomiting
  • Constipation
  • Diarrhea
  • Urinary urgency, frequency
  • Flatulence
  • Bloating
  • Low-grade fever



  • Since bacteria are responsible for the inflammation, antibiotics are the cornerstone of diverticulitis treatment. However, the latest evidence demonstrates that acute uncomplicated diverticulitis can be safely and effectively treated without antibiotics 9, 10.

  • What is the best antibiotic? The colon harbors many bacterial species. So antibiotic should be active against a wide range of bacteria, including Bacteroides and other anaerobic bacteria that grow best without oxygen, as well as E. coli and other aerobic (oxygen-requiring) gram-negative rods.
  • How long to take antibiotics? Antibiotic treatment should be continued for 7 to 10 days.

Antibiotics for Mild Diverticulitis

Mild diverticulitis can be treated with the following regimen:

  • A clear liquid diet
  • 7-10 days course of oral broad-spectrum antibiotic.

Generally, symptoms subside and disappear rapidly within 48-72 hours with treatment. After a few days, the patient can start a soft, low-fiber diet and use a psyllium seed preparation for softening stools. After one month, patients can be put on a high-fiber diet.

Fluoroquinolones plus Metronidazole

Fluoroquinolones are widely used in the treatment of diverticulitis, because of their excellent activity against aerobic Gram-negative bacteria. In addition fluoroquinolones are rapidly and almost completely absorbed from the gastrointestinal tract.

Fluoroquinolones are combined with metronidazole because they don't cover anaerobes. Metronidazole (Flagyl) is highly active against anaerobic bacteria.


Ciprofloxacin (Cipro) 500 mg twice daily plus metronidazole 500 mg 3-4 times per day for 7-10 days.

Levofloxacin (Levaquin) 500 mg daily plus metronidazole 500 mg 3-4 times per day for 7-10 days.

Moxifloxacin (Avelox) 400 mg daily. Moxifloxacin can be used as monotherapy for diverticulitis.

Trimethoprim-Sulfamethoxazole plus Metronidazole

Trimethoprim/sulfamethoxazole (Bactrim, Septra) targets aerobic Gram-negative rods and enterococci.

Dosage: Trimethoprim/sulfamethoxazole DS 160mg/800mg (1 double-strength tablet) twice daily plus metronidazole 500 mg 3-4 times per day for 7-10 days.

Amoxicillin/Clavulanic acid

Amoxicillin/clavulanic acid (Augmentin) is effective against both types of bacteria (anaerobic and aerobic) and is suitable as a single-agent regimen.

Dosage: Amoxicillin/clavulanic acid 875mg/125mg twice daily.


Rifaximin, a poorly absorbable broad-spectrum antibiotic, is a new promising treatment for uncomplicated diverticular disease7, especially when used in addition to dietary fibre supplementation.

Rifaximin is active against both Gram-positive and Gram-negative aerobic and anaerobic bacteria. Rifaximin can effectively improve symptoms and maintain periods of remission in patients with uncomplicated diverticular disease. This medication is very well tolerated.

Antibiotics for Severe/Complicated Diverticulitis

Severe disease requires hospitalization, intravenous antibiotics, and bowel rest. Hospitalization is recommended if a patient shows signs of significant inflammation, is unable to take oral fluids, is older than 85 years, or has significant comorbid conditions.


Cefoxitin (Mefoxin) and cefotetan (Cefotan), intravenous 2nd generation cephalosporins, cover anaerobes and can be used as a single-antibiotic therapy for severe diverticulitis.

In the treatment of acute colonic diverticulitis Cefoxitin and combination of gentamicin with clindamycin have similar efficacy and tolerability. Cefoxitin has advantage of its narrower antimicrobial spectrum and lower cost4.

3rd generation cephalosporins:

  • Ceftriaxone (Rocephin)
  • Ceftazidime (Fortaz)
  • Cefotaxime (Claforan)

plus metronidazole or clindamycin. Third-generation cephalosporins ensure Gram-negative coverage but don't cover anaerobes.

Ampicillin and Sulbactam

Ampicillin and sulbactam (Unasyn) covers aerobic gram-negative rods, anaerobes and enterococci.

Piperacillin and Tazobactam sodium

Piperacillin and tazobactam sodium (Zosyn) covers gram-negative rods, anaerobes and most enterococci. It is a reliable empiric treatment for serious intra-abdominal infections.

Ticarcillin and Clavulanate potassium

Ticarcillin and clavulanate potassium (Timentin) is active against most gram-positive and gram-negative bacteria and most anaerobes.



  • Ertapenem (Invanz)
  • Meropenem (Merrem)
  • Imipenem and cilastatin (Primaxin)

Carbapenems are the most effective antibiotics for complicated cases of diverticulitis because of increasing bacterial resistance to other medications.

Ertapenem 3-days regimen is very effective antibiotic therapy for localized mild to moderate intra-abdominal infections. Ertapenem is more effective than Ampicillin-Sulbactam5.

Meropenem is as effective and as well tolerated as imipenem/cilastatin in the treatment of moderate to severe intra-abdominal infections6.

Imipenem/cilastatin is very effective antibiotic in treating polymicrobial infections.


Tigecycline (Tygacil), an antibiotic with broad coverage, is a good choice in patients with severe penicillin allergy. Tigecycline is FDA approved for complicated intra-abdominal infections.



  • Gentamycin8
  • Tobramycin
  • Amikacin

plus metronidazole or clindamycin.

Aminoglycosides are particularly active against aerobic Gram-negative bacteria but are not active against anaerobes. Gentamicin is the most commonly used aminoglycoside, but amikacin may be particularly effective against resistant organisms.


Aztreonam plus metronidazole or clindamycin.

Aztreonam has no useful activity against anaerobes, but has very broad spectrum against Gram-negative aerobes, including Pseudomonas aeruginosa. Therefore in the treatment of complicated intra-abdominal infections aztreonam is used in combination with other antimicrobial medications.


  • 1. Beckham H, Whitlow CB. Diverticular Disease: The Medical and Nonoperative Treatment of Diverticulitis Clin Colon Rectal Surg. 2009 Aug;22(3):156-60. PubMed
  • 2. American Academy of Family Physicians. Diverticular Disease: Diagnosis and Treatment.
  • 3. Alonso S, Pera M, Parés D, Pascual M, Gil MJ, Courtier R, Grande L. Outpatient treatment of patients with uncomplicated acute diverticulitis. Colorectal Dis. 2010 Oct;12
  • 4. Kellum JM, Sugerman HJ, Coppa GF, Way LR, Fine R, Herz B, Speck EL, Jackson D, Duma RJ. Randomized, prospective comparison of cefoxitin and gentamicin-clindamycin in the treatment of acute colonic diverticulitis. Clin Ther. 1992 May-Jun;14(3):376-84.
  • 5. Catena F, Vallicelli C, Ansaloni L, Sartelli M, Di Saverio S, Schiavina R, Pasqualini E, Amaduzzi A, Coccolini F, Cucchi M, Lazzareschi D, Baiocchi GL, Pinna AD. T.E.A. Study: three-day ertapenem versus three-day Ampicillin-Sulbactam. BMC Gastroenterol. 2013 Apr 30
  • 6. Geroulanos SJ. Meropenem versus imipenem/cilastatin in intra-abdominal infections requiring surgery. J Antimicrob Chemother. 1995 Jul;36 Suppl A:191-205.
  • 7. Latella G, Scarpignato C. Rifaximin in the management of colonic diverticular disease. Expert Rev Gastroenterol Hepatol. 2009 Dec.
  • 8. Tursi A. Acute diverticulitis of the colon - current medical therapeutic management. Expert Opin Pharmacother. 2004 Jan;5(1):55-9. PubMed
  • 9. Isacson D, Andreasson K, Nikberg M, Smedh K, Chabok A. No antibiotics in acute uncomplicated diverticulitis: does it work? Scand J Gastroenterol. 2014 Dec;49(12) PubMed
  • 10. Brochmann N, Schultz JK1, Jakobsen GS, Oresland T. Management of acute uncomplicated diverticulitis without antibiotics: a single centre cohort study. Colorectal Dis. 2016 Apr 18. PubMed
  • 11. Janes SE, Meagher A, Frizelle FA. Management of diverticulitis. BMJ. 2006 Feb 4;332(7536):271–275

Last updated: November 07, 2017
Published: October 05, 2013

  • The majority of patients with colonic diverticulosis remain asymptomatic and do not require any treatment.
  • Most cases of acute uncomplicated diverticulitis are treated with conservative medical therapy.11


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