The objective of this study is to investigate the effect of Esomeprazol administered in tablets (Esomeprazol MUT Sandoz® 40mg) or in solution (Esomeprazol MUT Sandoz® 40mg in 10ml tap water) on acid production in the gastric pouch by measuring the intragastric pH and the serum concentration of esomeprazole.

To assess the clinical effect of the esomeprazole absorption after Roux-en-Y gastric bypass, we intend to measure the serum concentration after administration as intact capsules or open in solution and correlate it with the pH in the gastric pouch, measured with the wireless BRAVOTM capsule pH measurement system. The feasibility and safety of the wireless pH monitoring system has been shown before.

The patients who met all the inclusion criteria undergo a routine upper endoscopy one year after RYGB. At the end of the endoscopy, the wireless BRAVO™ - pH monitoring device is placed and the participant is discharged with ongoing pH monitoring. The next day, the participant is randomized to either receive Esomeprazol MUT Sandoz® tablet 40mg or Esomeprazol MUT Sandoz® 40mg in solution. Serum concentration of Esomeprazol is measured at 0, 60 and 120 minutes and the patient is discharged after. After 48 hours of pH monitoring, the patient returns the BRAVO™ - recorder, adverse events are assessed and the study is terminated.

Inclusion Criteria:

• Proximal Roux-en-Y gastric bypass with linear stapled anastomosis 12 months prior to the study investigation
• Routine administration of proton pump inhibitors for 6 months postoperatively
• No intake of proton pump inhibitors at least 4 weeks prior to study investigation
• No marginal ulcers in upper endoscopy prior to placement of wireless BRAVO™ pH monitoring capsule
• No symptoms related to gastro-esophageal reflux or marginal ulcers (i.e. epigastric pain, retrosternal burning, regurgitation)
• Informed consent as documented by signature

Exclusion Criteria:

• Known intolerance or allergy for Esomeprazol
• Contraindication for upper endoscopy
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant
• Women who are pregnant or breast feeding Major hepatic dysfunction