What are the recommended antibiotics (abx) for colorectal surgery?

From the Guidelines

For colon surgery, preoperative antibiotics should be administered within 60 minutes before surgical incision, with the recommended regimen being cefazolin 2g IV plus metronidazole 500mg IV, or alternatively, cefoxitin 2g IV or ertapenem 1g IV as a single agent, as supported by the most recent guidelines 1.

Key Considerations

• The choice of antibiotics should target both aerobic and anaerobic bacteria commonly found in the colon, including gram-negative organisms and anaerobes like Bacteroides fragilis.
• For patients with beta-lactam allergy, alternative regimens such as clindamycin 900mg IV plus gentamicin 5mg/kg IV, or aztreonam 2g IV, or ciprofloxacin 400mg IV can be used.
• The antibiotics should be redosed during surgery if the procedure exceeds two half-lives of the drug or if there is significant blood loss.
• Postoperative antibiotics should be discontinued within 24 hours after surgery unless there is evidence of infection.

Rationale

• The use of preoperative antibiotics in colon surgery has been shown to reduce the risk of surgical site infections (SSI) by decreasing the bacterial load at the surgical site 1.
• The recommended regimens are based on the most recent guidelines and take into account the potential benefits and risks of different antibiotics, including the risk of antibiotic resistance and allergic reactions.
• The choice of antibiotics should be individualized based on the patient's specific needs and medical history, including any allergies or previous reactions to antibiotics.

Supporting Evidence

• A Cochrane review published in 2014 found that the use of oral or intravenous antibiotic prophylaxis before colorectal surgery reduced the risk of SSI from 39% to 13% 1.
• A recent meta-analysis found that the addition of oral antibiotics to intravenous administration in patients with bowel preparation reduced the risk of SSI compared with intravenous coverage alone 1.
• The Australian Therapeutic Guidelines (2019) recommend cefazolin plus metronidazole for colorectal surgery, including appendicectomy, or cefoxitin single therapy as an alternative 1.
• The American Society of Health-Systems Pharmacists, Infectious Diseases Society of America, Surgical Infection Society, and Society for Healthcare Epidemiology of America (2013) recommend cefazolin as the antibiotic of choice for prophylaxis in most procedures, with metronidazole added for colorectal procedures 1.

From the FDA Drug Label

Prophylaxis of Surgical Site Infections Following Elective Colorectal Surgery Ertapenem was evaluated in adults for prophylaxis of surgical site infection following elective colorectal surgery in a multicenter, randomized, double-blind, non-inferiority clinical trial This trial compared a single intravenous dose of ertapenem (1 g) versus cefotetan (2 g) administered over 30 minutes, 1 hour before elective colorectal surgery The prophylactic success rates at 4 weeks posttreatment in the clinically evaluable population were 70.5% (244/346) for ertapenem and 57.2% (194/339) for cefotetan

Ertapenem for Surgical Prophylaxis in Colon Surgery

• The recommended dose for prophylaxis of surgical site infection following elective colorectal surgery is 1 g administered as a single intravenous dose 1 hour prior to surgical incision 2.
• Ertapenem has been shown to be effective in reducing the risk of surgical site infections in patients undergoing elective colorectal surgery, with a prophylactic success rate of 70.5% at 4 weeks posttreatment 2.

From the Research

Surgical Site Infections in Colon Surgery

• Surgical site infections (SSIs) are a significant concern in colon surgery, with rates as high as 30% 3.
• The use of prophylactic antibiotics has been shown to reduce the risk of SSIs in colon surgery 4.

Antibiotic Choice

• A study comparing cefotetan and cefoxitin found no significant difference in clinical response rates, with both antibiotics achieving a satisfactory response in over 88% of patients 5.
• Another study found that ceftriaxone/metronidazole was associated with a decreased rate of SSIs compared to cefoxitin or ertapenem 3.
• Cefotetan has been shown to have a broad spectrum of activity against Gram-negative aerobic and most clinically important Gram-positive and anaerobic bacteria 6.

Dosing and Administration

• A study examining the use of higher doses of cefotetan or cefoxitin in obese patients found no significant difference in SSI rates between 2g and 3g doses 7.
• The optimal timing and duration of antibiotic administration remain unclear, with some studies suggesting that oral antibiotics may be effective in reducing SSIs 4.

Key Findings

• Prophylactic antibiotics can reduce the risk of SSIs in colon surgery by up to 75% 4.
• The choice of antibiotic and dosing regimen may impact the risk of SSIs, with some studies suggesting that ceftriaxone/metronidazole may be more effective than cefoxitin or ertapenem 3.
• Further research is needed to determine the optimal antibiotic regimen and dosing strategy for colon surgery 4, 7.