SummaryThe pharmacokinetics, serum levels and tissue penetration of netilmicin were studied after a single intravenous injection of 6 mg/kg. 13 patients scheduled for elective colorectal surgery and for antibiotic prophylaxis were given a combination of netilmicin and a single dose of ornidazole (1000mg intravenously). Mean maximal (10 minutes) and last determined (24-hour) netilmicin serum levels were 24.4 ± 3.4 and 0.9 ± 0.5 mg/L, respectively. The ,8-phase elimination halflife was 413 ± 68 minutes, and the apparent volume of distribution and clearance were 0.51 ± 0.12 L/kg and 0.07 ± 0.02 L/min, respectively. In all patients, adequate tissue levels (;;' MIC90 of pathogens) were found in the abdominal wall and epiploic fat at the time of incision and in the colonic wall at the time of anastomosis. At the time of closure, all but I patient had adequate tissue levels in the abdominal wall and epiploic fat. Further studies are needed to fully determine the clinical implications of these results but, in view of its pharmacokinetic properties, netilmicin, in combination with ornidazole, can be considered for antibiotic prophylaxis.