4. Documented symptoms of gastroesophageal reflux disease (GERD) for longer than 6 months (regurgitation and/or heartburn which is defined as burning epigastric or substernal pain which responds to acid neutralization or suppression) which requires daily use of proton pump inhibitors (PPIs) or other anti-reflux drug therapy, who continue to have symptoms despite maximum medical therapy or are "intolerant" -severe side-effects (e.g. anaphylaxis or severe allergic reaction, recurrent C. difficile, severe hypomagnesaemia) to one PPI or mild/moderate side effect (e.g. nausea, vomiting, diarrhea or abdominal pain) to at least 2 PPIs of different chemical classes.