When Is the Optimal Time to Administer Antibiotics Prior to Surgery?

Albert B. Lowenfels, MD


August 26, 2008

The Timing of Surgical Antimicrobial Prophylaxis

Weber WP, Marti WR, Zwahlen M, et al
Ann Surg. 2008;247:918-926


Prophylactic antimicrobial therapy is now part of routine efforts to prevent surgical wound infection and is now administered within 2 hours of the skin incision. The authors conducted an observational study of 3836 surgical patients in a Swiss hospital to determine the optimal time for administration of antibiotics. After administration of a second-generation cephalosporin antibiotic, the overall wound infection rate was 4.7%, but there was significant variation depending on the exact time of administration. Patients who received an antibiotic injection within 30 minutes of skin incision had almost double the infection rate compared with patients receiving antibiotics 60 to 30 minutes before surgery. Similarly, patients receiving antibiotics during the earliest time period (120 to 60 minutes) had a 75% increase in infection rates.


Within the accepted 2-hour period of antibiotic prophylaxis, there appears to be a narrow central window during which wound infection rates are lowest. The apparent best time for antibiotic administration is neither too soon nor too late: 60 to 30 minutes before the skin incision appears optimal. However, these results, based on retrospective observational data, need to be confirmed in a prospective randomized trial before implementing this policy.