A placebo‐controlled trial to assess the effects of 8 days of dosing with rabeprazole versus omeprazole on 24‐h intragastric acidity and plasma gastrin concentrations in young healthy male subjects

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Abstract
Background: Rabeprazole (LY307640, E3810) is a new, potent, proton pump inhibitor. A single daily 20 mg dose significantly decreases 24‐h intragastric acidity. There are no data currently available directly comparing the effect of rabeprazole on 24‐h acidity with established proton pump inhibitors.Aim: To compare the effects of rabeprazole 20 mg o.m. and omeprazole 20 mg o.m. on 24‐h intragastric acidity and plasma gastrin concentration in a randomized, double‐blind, placebo‐controlled trial, in healthy H. pylori‐negative subjects.Methods: Twenty‐four healthy male volunteers, negative for H. pylori infection by serology and 13C‐urea breath test, were studied on the 1st and 8th day of dosing with either placebo, rabeprazole 20 mg or omeprazole 20 mg, once each morning, in a crossover fashion. On days 1 and 8, hourly intragastric acidity was measured by gastric aspiration for 24 h from 08.00 hours. On day 8, plasma gastrin concentrations were also measured hourly from 08.00 to 24.00 hours, then every 2 h thereafter.Results: A single dose of both rabeprazole and omeprazole significantly decreased 24‐h intragastric acidity compared with placebo. The 24‐h acidity on day 1 was significantly decreased for rabeprazole compared with omeprazole (331 vs. 640 mmol.h/L, P < 0.001), resulting in a significantly higher median 24‐h intragastric pH and longer times at which intragastric pH was> 3 and> 4. On day 8 of dosing, the decrease in 24‐h intragastric acidity was greater with rabeprazole than with omeprazole, but the difference was not statistically significant (160 vs. 218 mmol.h/L, P = 0.1). However, 24‐h plasma gastrin concentration (1687 vs. 1085 pmol.h/L, P < 0.01) and percentage time that intragastric pH was> 3 (69 vs. 59%, P = 0.008) and> 4 (60 vs. 51%, P = 0.03) were significantly greater.Conclusions: Rabeprazole 20 mg once daily has a significantly faster onset of antisecretory activity than omeprazole 20 mg once daily. After 8 days the differences in intragastric pH > 3 and> 4 holding times persisted, but there was no significant difference in 24‐h acidity.

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