Purpose: To chemically characterize the fluids available for drug dissolution in the upper gastrointestinal tract during the fasted state in humans, and to examine variations and potential gender differences regarding the physico-chemical properties of these fluids.
Methods: Twenty-four healthy volunteers, 12 females and 12 males, were intubated, and fluids from the stomach and upper jejunum were collected separately. Bulk pH, osmolality, electrolytes and total concentrations of bile acids and proteins were assessed. To study intraindividual variations, eleven of the individuals were studied on more than one occasion.
Results: The stomach and upper jejunal fluids varied significantly in all the measured entities, except the total concentration of proteins. The intraindividual variability was pronounced in some of the individuals, both in the stomach and the upper jejunum. We did not, however, observe any gender differences.
Conclusions: This study demonstrates the complex nature of the fluids available for drug dissolution in the stomach and the upper small intestine in humans. The results can be used when designing a more physiological in vitro dissolution media representative for the fasted state. When designing such a medium, we suggest that gender differences not be taken into account.