Post-prandial reflux suppression by a raft-forming alginate (Gaviscon Advance) compared to a simple antacid documented by magnetic resonance imaging and pH-impedance monitoring: mechanistic assessment in healthy volunteers and randomised, controlled, double-blind study in reflux patients R. Sweis*, E. Kaufman † , A. Anggiansah ‡ , T. Wong § , P. Dettmar ¶ , M. Fried † , W. Schwizer † , R. K. Avvari**, A. Pal †† & M. Fox †,‡‡ *Department of Gastroenterology, Guys and St Thomas’ NHS Foundation Trust, London, UK. † Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland. ‡ Oesophageal Laboratory, Guys and St Thomas’ NHS Foundation Trust, London, UK. § Department of Gastroenterology, Guys and St Thomas’ NHS Foundation Trust, London, UK. ¶ RD Biomed Limited, Castle Hill Hospital, Hull, UK. **Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, India. †† Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata, India. ‡‡ NIHR Nottingham Digestive Diseases Biomedical Research Unit, Nottingham University Hospitals NHS Trust, Nottingham, UK. Correspondence to: Dr M. Fox, NIHR Nottingham Digestive Diseases Biomedical Research Unit, Nottingham University Hospitals NHS Trust, Queen’ s Medical Centre, D Floor, West Block, Nottingham NG7 2UH, UK. E-mail: dr.mark.fox@gmail.com Publication data Submitted 7 March 2013 First decision 29 March 2013 Resubmitted 30 March 2013 Accepted 30 March 2013 SUMMARY Background Alginates form a raft above the gastric contents, which may suppress gastro- oesophageal reflux; however, inconsistent effects have been reported in mecha- nistic and clinical studies. Aims To visualise reflux suppression by an alginate–antacid [Gaviscon Advance (GA), Reckitt Benckiser, UK] compared with a nonraft-forming antacid using magnetic resonance imaging (MRI), and to determine the feasibility of pH-impedance mon- itoring for assessment of reflux suppression by alginates. Methods Two studies were performed: (i) GA and antacid (Alucol, Wander Ltd, Switzer- land) were visualised in the stomach after ingestion in 12 healthy volunteers over 30 min after a meal by MRI, with reflux events documented by manome- try. (ii) A randomised controlled, double-blind cross-over trial of post-prandial reflux suppression documented by pH-impedance in 20 patients randomised to GA or antacid (Milk of Magnesia; Boots, UK) after two meals taken 24 h apart. Results MRI visualized a “mass” of GA form at the oesophago-gastric junction (OGJ); simple antacid sank to the distal stomach. The number of post-prandial com- mon cavity reflux events was less with GA than antacid [median 2 (0–5) vs. 5 (1–11); P < 0.035]. Distal reflux events and acid exposure measured by pH- impedance were similar after GA and antacid. There was a trend to reduced proximal reflux events with GA compared with antacid [10.5 (8.9) vs. 13.9 (8.3); P = 0.070]. Conclusions Gaviscon Advance forms a ‘mass’ close to the OGJ and significantly suppresses reflux compared with a nonraft-forming antacid. Standard pH-impedance moni- toring is suitable for clinical studies of GA in gastro-oesophageal reflux disease patients where proximal reflux is the primary outcome. Aliment Pharmacol Ther ª 2013 Blackwell Publishing Ltd 1 doi:10.1111/apt.12318 Alimentary Pharmacology and Therapeutics