- Use of the following concomitant medications: medications that can affect gastrointestinal (GI) motility; other investigational drug use (30 day "washout" required); medications affecting visceral perception; antidepressants; selective serotonin reuptake inhibitors; opioids; narcotic analgesics; antispasmodic and anticonvulsant agents; insulin or other hypoglycemic therapy; thyroid hormones; central nervous system (CNS) depressants.