- Patients who are unable or unwilling to discontinue the use of prostaglandins (e.g. misoprostol), sucralfate, prokinetic agents (e.g. metoclopramide), anticholinergics, cholinergic agents or spasmolytics. Use of opiates may be continued if started at least 2 weeks before study admission and the dosage is consistent (± 25% for total opioid daily dose) throughout the study