¹Oita University Hospital, Hasama-machi, Japan

Abstract

Purpose: Omeprazole, proton pump inhibitor, is widely used in treatment of peptic ulcer, Gastro esophageal reflux disease and eradication of Helicobacter pylori. But the mechanism is not well understood. So we examined the effects of omeprazole on plasma levels of gastrointestinal peptides {somatostatin, gastrin, motilin, vasoactive intestinal peptide (VIP), substance P (SP) and calcitonin gene related peptide (CGRP)}. Methods: Omeprazole or placebo was orally administered in five healthy male volunteers aged 25-30 years. Venous blood samples were taken before and at 30, 60, 90, 120, 180, 240 and 360 min after administration of the drug. Plasma peptide levels were measured using a sensitive enzyme immunoassay. Results: Omeprazole (20mg) causes significant increase in somatostatin-IS at 60-240 min compared with the response of the placebo treated group. Furthermore omeprazole showed 35.1 % (60min) increase of placebo motilin levels and 38.5 % (60min) inhibition of placebo gastrin levels. But omeprazole had no effect on plasma VIP-IS, SP-IS and CGRP-IS levels compared with the placebo treated groups. Conclusions: In this study, omeprazole enhanced somatostatin-IS levels. Somatostatin, a polypeptide, which distributes widely in the gastrointestinal tract, participates in the control of gut motility and hormones secretion. Omeprazole might have pharmacological mechanism not only inhibition of gastric acid secretion but also regulation of gastrointestinal peptide.