The authors compare the pharmacokinetic profiles, safety, and tolerability of rabeprazole, a new proton pump inhibitor (PPI), in healthy volunteers and in subjects with stable, endstage renal failure. This single-center open-label trial included two groups of subjects: 10 healthy males with 24-hour creatinine clearance greater than or equal to 90 mL/min/m(2) and 10 males with renal failure (24-hour creatinine clearance less than or equal to 5 mL/min/m(2)) receiving hemodialytic therapy. Normal subjects received a single, oral 20 mg rabeprazole dose. Those with renal failure received a 20 mg dose of rabeprazole on the day after hemodialysis and a second dose after a a-week washout period during dialysis. Blood samples were drawn before and up to 24 hours after rabeprazole administration for determination of plasma rabeprazole concentrations by high-performance liquid chromatography. Safety and tolerability of rabeprazole were determined by reporting adverse events and comparing vital signs, EGG, physical examinations, and clinical laboratory tests before and during treatment. Comparison of pharmacokinetic results from healthy volunteers with those from subjects with renal failure indicated no clinically significant differences between groups. In addition, there were no statistically significant differences between any pharmacokinetic parameters recorded during or after hemodialysis. Rabeprazole was well tolerated by both groups. Only two drug-related adverse events were reported, and there were no significant treatment-emergent changes in vital signs or EGG. Treatment-emergent changes in hematologic and clinical chemistry parameters were observed for a few subjects in each group and generally represented only slight deviations from the normal range. These results indicate that no dosage adjustment of rabeprazole is required in patients with renal dysfunction. These findings and the well-documented clinical efficacy of this new PPI in patients with gastric ulcers, duodenal ulcers, or gastroesophageal reflux disease support rabeprazole's use in the treatment of patients with acid peptic disorders. Journal of Clinical pharmacology, 1999;39:927-933 (C) 1999 the American College of Clinical Pharmacology.