As exenatide slows the rate at which materials leave the stomach, it is likely to alter the rate of intestinal absorption of oral drugs when administered within a certain timeframe relative to exenatide. In addition, the residence time within the stomach of other medication may be prolonged and data from this study will help assess the change in residence time in the presence of therapeutic doses of exenatide. This study will also evaluate the relationship between blood levels of exenatide and parameters measuring rate of stomach emptying.