Explore the impact of chronological age, proton pump inhibitors (PPIs) in older adults, and Type II diabetes in older adults on pH, buffer capacity, individual bile acid concentrations, and osmolality in the contents of the descending part of the duodenum during fasting, to evaluate whether drug disposition in the upper small intestine of relevant individuals is likely to differ from healthy adults.

After overnight fasting from food and water, contents of the second part of the duodenum from 17 adults who were free of conditions that confound the luminal physicochemical characteristics of interest (27–43 years, Reference Group), from 34 older adults (65–91 years, Test Group 1), from 20 older adults on PPIs (68–84 years, Test Group 2), from 10 diabetic older adults (68–79 years, Test Group 3), and from 7 diabetic older adults on PPIs (67–82 years, Test Group 4) were aspirated and characterized. In all Test Groups, individuals were non–frail and free of additional conditions that confound the luminal physicochemical characteristics of interest.

Median [range] pH values in the Reference Group were 7.83 [2.36–8.58] in line with previous observations in the descending duodenum during fasting. In all Test Groups, the median pH was slightly higher than 8. Median [range] values of buffer capacity in the Reference Group were 13.76 [3.36–67.80] mmol HCl/L/ΔpH. Median buffer capacity values in the Test Groups ranged from 6.88 to 17.01 mmol HCl/L/ΔpH. The predominant bile acids in all groups were glycocholic acid and glycochenodeoxycholic acid, in line with previous observations in healthy adults. The median total bile acid content in the Reference Group was in line with previous estimates in young adults and slightly lower than the medians of the Test Groups (1.98 vs. 2.26–3.48 mM). Although osmolality does not seem to be affected by chronological ageing, PPIs decrease mean osmolality in older adults (274 vs. 333 mOsmol/kg), in line with previous observations in adults.

Based on data collected in this study, the effect of chronological age, PPIs in older adults and/or Type II diabetes in older adults on the pH, buffer capacity or bile acids concentrations in the fasted duodenal contents appears to be too small to impact oral drug absorption.