The pharmacokinetics and safety of TY-11345 [(+/-)-2-[(4-methoxy-6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridin-9- yl)sulfinyl]-1H-benzimidazole sodium salt], a novel gastric proton pump inhibitor, were studied in healthy male volunteers after single (20, 40, and 80 mg) and repeated oral doses (60 mg, once daily for 7 days) as enteric-coated tablet. At the single doses of 20 and 40 mg, intragastric pH was continuously monitored in each of two subjects. No abnormal findings definitely attributable to the test drug were observed throughout the study. In the single-dose study, the maximum plasma concentration (Cmax) and area under the plasma concentration-time curve of TY-11345 increased in a dose-proportional manner. The time to reach Cmax was about 3 h after dosing and plasma concentrations declined thereafter with a half-life of about 1 h irrespective of dose. The effect of food intake on the pharmacokinetic parameters of TY-11345, which was evaluated at the dose of 40 mg in a cross-over design, was not significant. TY-11345 was not detected in urine unchanged, while a main metabolite and its conjugate were identified in urine as 32-38% of the dose. An intragastric pH value over 4 was obtained about 3 h after the administration of 40 mg and maintained for more than 5 h, despite the fall of plasma concentration. This effect was less obvious at a dose of 20 mg. In the multiple-dose study, the pharmacokinetics exhibited no substantial difference between the first and last doses.(ABSTRACT TRUNCATED AT 250 WORDS)