Do antibiotics contribute to postoperative ileus? Contractile responses of ileum smooth muscle in guinea pigs to long-term parenteral ceftriaxone and ampicillin

Background: Antibiotics may impair small bowel smooth muscle contractility and contribute to postoperative ileus. The aim of this study was to compare the contractile responses of ileum smooth muscle to different agonists in guinea pigs treated with ceftriaxone (Rocephin; F. Hoffman-La Roche, Kaiseraugst, Switzerland) or ampicillin (Ampisina; Mustafa Nevzat Ilac Sanayii AS, Istanbul, Turkey). Methods: Twenty-four adult guinea pigs were randomly divided into three groups. Whereas eight of these received ceftriaxone sodium (100 mg/kg per day, i.m.) for 10 days, another eight guinea pigs received ampicillin (50 mg/kg per day, i.m.) for 10 days and the remaining eight served as the control group receiving 1 mL distilled water during 10 days as placebo. By the end of 10 days, the animals were killed and their ilea were excised. Ileum segments were placed in an organ bath; concentration-response relationship for carbachol and histamine were obtained by adding the reagent cumulatively to the bath. Results: pD(2) values being the same, maximum contractile responses (E-max) to carbachol and histamine were significantly reduced in the ceftriaxone sodium group compared with the control group. No significant differences in E-max and pD(2) values to carbachol and histamine were observed between the ampicillin group and the control group. Conclusion: These data indicate that whereas ceftriaxone may impair small bowel smooth muscle contractility, ampicillin does not. There are implications for the long-term use of parenteral antibiotics in the postoperative period.