The aim of the study is to identify the best method of omeprazole (OME) application with respect to intragastric pH, cytochrome P450 2C19 (CYP2C19) genotype and phenotype.

The patients with non-variceal upper gastrointestinal bleeding (NVUGIB) are prospectively enrolled. After the achievement of endoscopic hemostasis, the patients are randomized to 40-mg intravenous (i.v.) OME bolus injection every 12 h or 8-mg/h continuous i.v. infusion for 72 h after an 80-mg i.v. OME bolus administration. The intragastric pH is recorded for 72 h. The CYP2C19 variant alleles (*2, *3, *17) are analyzed and the serum concentrations of OME and 5-hydroxyomeprazole (5-OH OME) are determined. The diagnosis of Helicobacter pylori infection was based on the results of the rapid urease test performed on stomach mucosa biopsies (antrum and angle) and on the results of the stool antigen test.

Inclusion Criteria:

• written informed consent must be obtained before any treatment or assessment is performed
• patients admitted with upper gastrointestinal bleeding (UGIB) symptoms to the Emergency Department of the University Hospital of Bialystok (Bialystok, Poland)

Exclusion Criteria:

• pregnancy
• age >90 years
• lack of written consent
• recent treatment with certain medications, including PPIs, H2-receptor antagonists (H2RA), antacids, steroids, oral contraceptives, clopidogrel, prasugrel and clarithromycin
• the presence of variceal UGIB
• history of surgery of upper gastro-intestinal tract