 3. Unable to withdraw all medications 48 hours prior to Visit 1; any medication that alters GI transit including but not limited to laxatives, magnesium or aluminum-containing antacids. prokinetics, erythromycin, narcotics, anticholinergics, tricyclic antidepressants and SNRIs; analgesic drugs including opiates, NSAIDs, and COX-2 inhibitors Note: Tylenol is permitted, GABAergic agents and benzodiazepines. 