- Ongoing therapy with drugs known to affect gut motility, such as prokinetic agents (such as metoclopramide, domperidone, erythromycin, azithromycin), anti-emetic agents, anxiolytics (such as benzodiazepines), antidepressive agents (such as trycyclics, SSRI's etc.), narcotic analgesic agents (such as methadone, fentanyl), anticholinergic agents for IBS, medications for constipation (including enemas, cathartics, polyethylene glycol solutions), 5HT3 antagonists, anti-diarrheal agents (such as loperamide), opiate agents used to treat diarrhoea, NSAIDs (more than once daily), other antibiotics taken during or within 4 weeks of study onset, magnesium-containing antacids