CYP2B6 and gastroesophageal reflux disease: The etiology of RGERD is multifactorial, involving multiple mechanisms, including impairment of the esophageal anti-reflux barrier, decreased esophageal clearance, esophageal motility disorders, duodenogastric esophageal reflux, gastric emptying disorders, insufficient acid suppression, increased P450-specific isoenzyme metabolism, hiatal hernia, non-acid reflux, and psychological factors.