Objective: To evaluate and compare the pharmacodynamic effects of IY-81149 and omeprazole on gastric pH in patients with gastroesophageal reflux disease. Methods: Sixty male and female volunteers with gastroesophageal reflux disease were enrolled in a double-blind, two-way, crossover, dose-ranging study. Subjects were randomized into three groups, with each group comparing the effect of one of three doses of IY-81149 (5, 10, or 20 mg) with 20 mg omeprazole. IY-81149 and omeprazole were administered once daily for 5 days. Continuous 24-hour pH measurements were performed before the first dose (baseline) and after the fifth dose in both periods. Gastric acid suppression was evaluated on the basis of the following parameters: AUC(0-24), median pH in a 24-hour interval (pH(median)), and the percent time in a 24-hour interval in which the gastric pH was greater than 4 (t(pH > 4)). The truncated AUC parameters AUC(0-8), AUC(8-16), and AUC(16-24) were also calculated. The effects of IY-81149 and omeprazole on gastric pH were compared by nse of analyses of covariance. The dose-response relationship for IY-81149 was also evaluated. Results: There were no statistically significant differences between 5 mg IY-81149 and 20 mg omeprazole in terms of AUC(0-24), pH(median), t(pH > 4), AUC(0-8), and AUC(8-16). IY-81149, at 10 mg, produced a significantly greater gastric acid suppression than omeprazole on the basis of the values of AUC(0-24), pH(median), t(pH > 4), AUC(8-16), and AUC(16-24). Administration of 20 mg IY-81149 produced a significantly greater gastric acid suppression on the basis of all parameters. All doses of IY-81149 were more effective than omeprazole during 16 to 24 hours after the dose was administered. Conclusions: Administration of 10 and 20 mg IY-81149 produced a statistically significantly greater and prolonged suppression of gastric pH than 20 mg omeprazole.
