Prophylactic regimens in colorectal surgery: An open, randomized, consecutive trial on metronidazole used alone or in combination with ampicillin or doxycycline

In 17 Scandinavian hospitals, an open, randomized, consecutive trial was made on the use of prophylactic antibiotics in colorectal surgery. Metronidazole used alone was compared with metronidazole supplemented by ampicillin or doxycycline. Each type of drug was given as a single preoperative intravenous infusion. With metronidazole alone, postoperative infection occurred in 12.9% of all patients. This figure was significantly reduced to 3.2% by adding ampicillin or doxycycline to the prophylactic regimen (p=0.01). The additional effect achieved by ampicillin or doxycycline was due to a significant reduction of wound infections in cases of rectal surgery. For operations on the right and left colon, no significant improvement was obtained by adding ampicillin or doxycycline to metronidazole (p=0.19). For no type of colorectal surgery was there any significant difference in infection rate between patients who received metronidazole plus ampicillin and those who were given the combination of metronidazole and doxycycline. It is concluded that ampicillin and doxycycline are equally effective. Ampicillin is recommended, however, due to the increasing selection of tetracycline‐resistant bacteria. One single preoperative infusion of each drug gave the same effect as found in a previous study after multiple infusions, the first of them being given preoperatively. It is concluded that a satisfactory prophylactic effect is obtained by a single preoperative infusion of antimicrobial drugs directed against anaerobic as well as aerobic bacteria.