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Antibiotics for Diverticulitis

What is a Diverticulitis?

Diverticulitis is an inflammation of one or more diverticula, which are small pouches created by herniation of mucosa into the wall of the colon.

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

Signs & Symptoms

Signs and symptoms of diverticulitis depend on the location of the affected diverticulum, the severity of the inflammatory process, and the presence of complications.

The most common symptoms are:

  • Left lower quadrant pain (70% of patients)
  • Change in bowel habits
  • Nausea and vomiting
  • Constipation
  • Diarrhea
  • Flatulence
  • Bloating

Mild Diverticulitis

Patients with mild diverticulitis can be treated with the following regimen:

  • A clear liquid diet
  • 7-10 days of oral broad-spectrum antimicrobial therapy.

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 (e.g., Metamucil and Citrucel) daily to keep the stool soft. After one month, patients can begin a high-fiber diet.

Severe Diverticulitis

Severe disease requires hospitalization, bowel rest, and intravenous antibiotics. Hospitalization is recommended if patients show signs of significant inflammation, are unable to take oral fluids, are older than 85 years, or have significant comorbid conditions.


Since bacteria are responsible for the inflammation, antibiotics are the cornerstone of diverticulitis treatment.

What is the best antibiotic? Because the colon harbors many bacterial species, antibiotic should target a broad 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 should antibiotics be given? Antibiotic treatment should be continued for 7 to 10 days.

Antibiotics for Mild Diverticulitis

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 must be combined with metronidazole because they don't cover anaerobes. Metronidazole (Flagyl) is active against various 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 a single agent for diverticulitis and does not need metronidazole.

Trimethoprim-Sulfamethoxazol 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 is a new promising therapy for uncomplicated diverticular disease7, especially when used in addition to dietary fibre supplementation.

There is new evidence that the poorly absorbable, broad-spectrum, oral antibiotic, rifaximin, is effective against both Gram-positive and Gram-negative aerobic and anaerobic bacteria. Multiple studies have demonstrated that rifaximin can effectively improve symptoms and maintain periods of remission in patients with uncomplicated diverticular disease, while also being very well tolerated.

Antibiotics for Severe/Complicated Diverticulitis


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

Cefoxitin has efficacy and tolerability similar to that of gentamicin with clindamycin combination in the treatment of acute colonic diverticulitis and may be preferred because 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 option for the empiric treatment of high risk intra-abdominal infections.

Ticarcillin and Clavulanate potassium

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

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

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

Ertapenem 3-days regimen is very effective antibiotic therapy for localized intra-abdominal infections ranging from mild to moderate severity.

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.



  • Gentamycin
  • Tobramycin
  • Amikacin

plus metronidazole or clindamycin. Aminoglycosides provide Gram-negative coverage but are not active against anaerobes.

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 it is not used as a single agent.

  • 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. Kellum JM, Sugerman HJ, Coppa GF, Way LR, Fine R, Herz B, Speck EL, Jackson D, Duma RJ.
  • 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.

Published: October 05, 2013
Last updated: October 05, 2013

  • The majority of patients with colonic diverticulosis remain asymptomatic and do not require any treatment.
  • Acute uncomplicated diverticulitis is successfully treated in 70-100% of patients with conservative management.