2. Use of any drugs that may affect GI motility such as laxatives, stool softeners, promotility agents, products to prevent diarrhea, purgatives and enemas during the study. Non-systematically absorbed medications (e.g. milk of magnesia, MiralaxTM) can be held for 24 hours prior to taking the study medication. Systematically absorbed medications can be held based upon their half-life and length of activity.