Reduced bioavailability of oral metronidazole in postoperative ileus

Abstract EN

Background: Metronidazole has been reported to reduce postoperative anaerobic infections following surgical procedures.

Because of high cost and poor availability of intravenous metronidazole compared with that of oral preparation, we decided to measure the serum level of metronidazole after oral administration in patients during postoperative ileus, and to evaluate the substitution of intravenous metronidazole for the oral product. Methods: The present study comprised 45 adult patients undergoing major abdominal surgery via long laparatomy incision from Aug to Nov 2003. (500 mg of Metronidazole was administered as a single dose orally to each patient twice, one in ileus condition and the other in nonileus condition.

Blood sampling was done 1 hour after each episode of the drug administration). Results: A significant reduction (P<0.001) was found between the mean serum metronidazole concentration (2.90 ± 2.29 SD g/ml) during postoperative ileus, and that of controls (11.07±6.72 SD g/ml).

In majority of patients (62.5%), the serum level of metronidazole in ileus did not reach its minimum inhibitory concentration (3 µg/ml) for the most clinically important anaerobic bacteria. Conclusions: Postoperative ileus significantly affected the oral absorption of metronidazole.

As a result, if we want to control an active anaerobic infection with a prompt antibiotic therapy, it seems that initiating of the therapeutic regimen with oral Metronidazole postoperatively is not justified.