Pharmacokinetics of ornidazole in patients with renal insufficiency; influence of haemodialysis and peritoneal dialysis.

The pharmacokinetics of ornidazole (Tiberal) was studied after intravenous administration of a single 500 mg dose in eight patients with advanced chronic renal failure (ACRF) (creatinine clearance 2‐16 ml/min), in seven patients treated by haemodialysis (residual renal creatinine clearance 0‐5 ml/min) and in five patients treated by continuous ambulatory peritoneal dialysis (CAPD) (residual renal creatinine clearance 0‐6 ml/min). In ACRF patients, the half‐life of ornidazole was 10.8 +/‐ 1.4 h, the total plasma clearance 46.3 +/‐ 2.3 ml/min and the volume of distribution 0.73 +/‐ 0.06 l/kg. During haemodialysis, ornidazole was partly removed: the dialyser extraction ratio was 42 +/‐ 5% and the dialysis clearance 64 +/‐ 7 ml/min. During CAPD, peritoneal excretion was low: the dialysis clearance was 3.0 +/‐ 0.4 ml/min and in 48 h 6.0 +/‐ 1.1% of the administered dose was found in the peritoneal fluids. In these patients, the half‐life of ornidazole was 11.8 +/‐ 0.8 h and total plasma clearance was 48.3 +/‐ 5.5 ml/min, values which were close to those determined in non dialysed patients. In patients with end‐stage renal disease, the half‐life of ornidazole is comparable to that of subjects with normal renal function. This is due to the predominantly extra‐renal elimination of the drug. Therefore, there is no need to modify the usual dosage of ornidazole for these patients. Because of the large elimination of the drug during haemodialysis it is necessary to administer the drug after the dialysis session.