Acid-Suppressive Effects of Various Regimens of Omeprazole in Helicobacter pylori-Negative CYP2C19 Homozygous Extensive Metabolizers: Which Regimen Has the Strongest Effect?

To achieve more potent and long-lasting acid suppression, omeprazole was administered for 7 days in 5 regimens: 10, 20, and 40 mg once daily (od), and 10 and 20 mg twice daily (bid), in 7 healthy Helicobacter pylori-negative CYP2C19 homozygous extensive metabolizers, and intragastric pH was continuously measured. The median intragastric pH and percent time pH > 4.0 for 24 hours increased dose dependently with 10, 20, and 40 mg od. Ten and 20 mg bid wre comparable to 20 and 40 mg od, respectively. Concerning percent time pH > 4.0 in the nighttime (20:00–8:00 hours), 20 mg bid was significantly superior to 40 mg od (P < .05). In 4 of the 5 regimens, all 7 subjects had nocturnal acid breakthrough, whereas with 20 mg bid it occurred in only 3. We concluded that, considering nighttime acid suppression, omeprazole 20 mg bid had the strongest effect.