The muscarinic antagonist tolterodine is widely used treat urinary urge incontinence. Though acteylcholine is the primary excitatory neurotransmitter in the gastrointestinal tract, the phase III trials suggest that tolterodine infrequently causes constipation. Therefore, the objectives of this study are to assess if tolterodine affects the speed at which food travels through the stomach, intestines and colon (i.e., gastrointestinal and colonic transit) in healthy subjects.

The specific aims of this study are to test the hypotheses that the non-specific muscarinic antagonist tolterodine will not:- i) delay colonic transit and the proximal colonic emptying rate; ii) delay gastric emptying; nor iii) delay small intestinal transit compared to placebo in healthy subjects.

Age 18-70 years old. Absence of gastrointestinal symptoms as characterized by bowel symptoms questionnaire and absence of significant anxiety or depression characterized by a hospital anxiety and depression questionnaire.

Able to understand and willing to sign informed consent. Females who are nonpregnant, nonlactating, and willing to use a clinically approved methods of contraception two weeks prior to Day 0 until 1 week after the last dose of study medication.