The purpose of this study is to assess the pharmacodynamics (intragastric pH) after repeated oral administration of D961H 10 mg and omeprazole 10 mg in Japanese healthy male subjects who are classified by the genotype of CYP2C19 by the assessment of percentage of time with intragastric pH>4 during 24 hours after dose on day 5.

Inclusion Criteria:

• Healthy Japanese male subjects between 20 and 45 years of age
• Genotype of CYP2C19 has been known as the volunteer panel data
• H. pylori negative has been known by urea breath test as the volunteer panel data.

Exclusion Criteria:

• Significant clinical illness from the 2 weeks preceding the pre-entry visit to the randomisation, as judged by the investigator(s), eg, acute inflammatory disease which requires medical intervention
• Past or present cardiac, renal, hepatic, neurological or gastrointestinal disease, as judged by the investigator(s), eg, sequelae of myocardial infarction, nephritis, hepatitis and cerebral infarction
• Past or present severe allergic disease, hypersensitivity to food or drugs (except for seasonal hay fever), or allergic symptoms requiring medical intervention (eg, anesthetics used at the intragastric pH measurement)