Comparison of concentrations of two doses of clavulanic acid (200 and 400 milligrams) administered with amoxicillin (2,000 milligrams) in tissues of patients undergoing colorectal surgery

Abstract

The concentrations of clavulanic acid and amoxicillin were determined in sera and different abdominal tissues of 17 patients who underwent elective colorectal surgery. Patients were randomly allocated to two groups. At the time of induction of anesthesia, patients in group 1 were given 200 mg of clavulanic acid with 2,000 mg of amoxicillin and patients in group 2 received 400 mg of clavulanic acid with 2,000 mg of amoxicillin. In both groups, the initial dose was administered again after 2 h. Blood samples were collected to determine peak and trough antibiotic levels. Serial blood samples were also collected at predetermined periods (opening and closure of the abdominal cavity and surgical anastomosis). Abdominal wall fat, epiploic fat, and colonic wall tissue samples were collected simultaneously. Antibiotic concentrations were determined by high-performance liquid chromatography. Increasing the dose of clavulanic acid to 400 mg resulted in significantly higher peak and trough levels in serum (P < 0.03). Following the injection of 400 mg, mean concentrations of clavulanic acid in the fatty tissues were significantly increased at the time of opening (P < 0.02). The concentrations of clavulanic acid and amoxicillin in fatty tissues were 17 to 52% and 12 to 23% of the levels in sera, respectively. In the colonic wall, the concentrations of clavulanic acid and amoxicillin were 52 to 63% and 49 and 27% of the levels in sera, respectively. In sera, clavulanic acid given at a dose of 200 or 400 mg reached or exceeded the concentrations found to be effective in vitro to reduce the MICs of amoxicillin from the resistant to the susceptible category for 90% of the potential pathogens. In most of the tissues investigated, increased the dose of clavulanic acid to 400 mg resulted in a significantly higher number of samples with concentrations found to be effective in vitro (72 versus 11%; P < 0.05). In conclusion, increasing the dose of clavulanic acid to 400 mg resulted in higher levels in sera and improved penetration into the abdominal tissues in patients undergoing colorectal surgery.