Assessment of the dynamic nature of upper gastrointestinal pH: A pooled analysis using the fluid aspiration technique

This manuscript compiles a set of temporal pH profiles of the upper gastrointestinal (GI) tract under varying physiological and pharmacological conditions, including water and food intake as well as proton pump inhibitor (PPI) co-medication. A pooled analysis was conducted using data from 19 clinical studies previously performed in our laboratory, all of which employed standardised protocols and measurement techniques. Intraluminal pH was recorded in aspirated samples from the gastric antrum, duodenum, and proximal jejunum. Test conditions involved administering 240 to 250 mL of water in either the fasted state, the fed state after intake of the nutritional supplement Ensure Plus, or the fasted state with co-medication of esomeprazole. Trends in time-dependent pH were visualised using generalised additive models for location and shape (GAMLSS). Fed state profiles showed different temporal pH developments compared to the fasted state post water ingestion in the stomach and duodenum. An exploratory analysis using an FDA-standard high-fat breakfast yielded pH profiles similar in shape to those with Ensure Plus, though with a trend towards lower median pH values. Co-administration of esomeprazole resulted in pH increases not only in the stomach but also in the duodenum and jejunum, compared to the fasted state. These findings provide detailed insight into the dynamic luminal pH environment of the upper GI tract, potentially relevant to the design, optimisation, and evaluation of oral dosage forms. Furthermore, the provided data may support the development and refinement of in silico tools used to predict oral drug behaviour.