Ranitidine pharmacokinetics in continuous ambulatory peritoneal dialysis.

Ranitidine kinetics in renal failure were evaluated in six patients undergoing continuous ambulatory peritoneal dialysis (CAPD). On separate occasions each patient received either 50 mg intravenously (i.v.) or 150 mg orally of ranitidine HCl. Following i.v. administration, the plasma concentration vs time curve was best described by a two compartment model with firstorder elimination. The mean +/- SD distribution and elimination rate constants were 2.47 +/- 0.78 and 0.098 +/- 0.013 h, respectively. The area under the serum concentration vs time curve after the i.v. dose was 5979 +/- 2870 micrograms X h X l-1, resulting in a mean volume of distribution of 76.8 l and a total body clearance of 126 ml X min-1. Following oral administration the observed maximum plasma concentration was 904 +/- 483 micrograms X l-1 at 4.2 +/- 1.8 h, and the bioavailability was 69.7 +/- 35.6%. The peritoneal clearance of ranitidine was 3.2 +/- 0.7 and 2.6 +/- 0.6 ml X min-1 for the i.v. and oral groups, respectively. The amount of drug removed by dialysis was 561.2 +/- 336.2 micrograms for the i.v. and 1197.1 +/- 602.3 micrograms for the oral group. Four patients in the i.v. group had urine output during the study period with renal ranitidine clearance values of 9.9 +/- 9.9 ml X min-1. Two patients in the oral group had urine output and corresponding renal ranitidine clearance values of 5.1 and 20.1 ml X min-1. A dosage regimen for ranitidine is proposed based on ranitidine kinetics in patients undergoing CAPD.