Ceftriaxone: renal and biliary excretion and effect on the colon microflora

Renal and biliary clearance of ceftriaxone were simultaneously determined in four healthy male volunteers during constant iv infusion to steady state. The biliary secretion of ceftriaxone into the duodenum was measured using a duodenal marker-perfusion technique. The renal clearance of ceftriaxone varied between 4–13ml/min, and was independent of variations in plasma concentration of ceftriaxone from 3 to 84 mg/l. The biliary clearance of ceftriaxone varied between 1–13 ml/min. At least 11% of the dose was excreted in bile in unchanged form. Faecal samples were collected before the experiment and on days 1, 3 and 10 after the infusion for determination of ceftriaxone concentration and cultivation of aerobic and anaerobic bacteria and yeasts. Pronounced suppression of the aerobic and anaerobic colon flora was observed. All volunteers were colonized by potentially pathogenic bacteria and yeasts. The bowel microflora returned to normal in all subjects after ten days.