The effect of omeprazole on gastric juice viscosity, pH and bacterial counts.

Background: In vitro studies have shown that pH is an important determinant of mucus structure and function, but the relationship in vivo is unclear. Omeprazole increases intragastric pH and also allows bacterial overgrowth. In this study we have assessed the effect of omeprazole on gastric juice viscosity and examined the influence of pH and bacterial overgrowth on the resulting change.
Methods: Gastric juice specific viscosity, pH and total bacterial counts were measured in nine healthy male volunteers before and after omeprazole 20 mg twice daily for 1 week. The effect of incubation at pH 2 and 7 was also determined. Viscosity changes were compared with changes in pH and bacterial counts.
Results: Mean viscosity fell (P < 0.05) following treatment, though there was a wide range in viscosity both before and after treatment. The decrease was reproduced by incubation of pre-treatment juice at pH 7 but not pH 2. The fall in viscosity was correlated (P < 0.05) with change pH.
Conclusion: Omeprazole decreases gastric juice, and hence gastric mucus, viscosity by increasing intragastric pH. This could be important if it allows improved penetration of antimicrobials to Helicobacter pylori within the mucus layer.