Characteristics of the Human Upper Gastrointestinal Contents in the Fasted State Under Hypo- and A-chlorhydric Gastric Conditions Under Conditions of Typical Drug - Drug Interaction Studies

Evaluate the impact of reduced gastric acid secretion after administration of two acid-reducing agents on the physicochemical characteristics of contents of upper gastrointestinal lumen of fasted adults. Eight healthy male adults, fasted from food for 12 h, participated in a three-phase crossover study. Phase 1: No drug treatment prior to aspirations. Phase 2: Oral administration of 40 mg pantoprazole at ~9 am the last 3 days prior to aspirations and at ~7 am on aspiration day. Phase 3: Oral administration of 20 mg famotidine at ~7 pm prior to aspirations and at ~7 am on aspiration day. Samples from the contents of upper gastrointestinal lumen were aspirated for 50 min, after administration of 240 ml table water at ~9 am. Reduction of gastric acid secretion was accompanied by reduced buffer capacity, chloride ion concentration, osmolality and surface tension in stomach and by increased pH (up to ~0.7 units) in upper small intestine during the first 50 min post-water administration. The mechanism of reduction of acid secretion seems to be important for the buffer capacity in stomach and for the surface tension in upper gastrointestinal lumen. Apart from gastric pH, reduced acid secretion affects physicochemical characteristics of contents of upper gastrointestinal lumen which may be important for the performance of certain drugs/products in the fasted state.