My son was diagnosed with GERD in 2001, and he was given Omeprazole. It did not help and caused unexplained weight loss. His endoscope and CT of the abdomen were normal. He still has pain in the middle of his chest, and is unable to eat comfortably. He is now on Dexilant.
By the time he is 30, they will cripple him. Here is the problem: That stomach acid was not put there by accident. When you start removing it, you take away several important things. Probably the most important thing for him is the ability to digest proteins, because without acid, pepsin, trypsin, and chymotrypsin, are inactivated. If he is losing weight, it is because he is malnourished.
More than that, when you treat for somebody for reflux esophagitis or gastroesophageal reflux disease, which is what GERD stands for, the real issue is not the acid at all. It is the lower esophageal sphincter tone.
It could be Irritable Bowel Disorder (IBS). What can you do for inflammatory bowel disease? More times than not, by giving them antibiotics, it makes IBS worse because it changes the gastric flora. It changes the organisms that are in the gut. Sometimes it changes it and it does not change back, and that is probably what has happened in this case. When that occurs, digestion gets even less effective.
My suggestion to you would be to switch him away from Dexilant and get him on something called Sucralfate. It is an old medication. It is a complex sugar that does not get absorbed and it is almost like using chemical band-aids on the inside of the gut. It sticks to the GI tract where the esophagus is irritated, and allows it to heal. Then, you add something called L-Glutamine. The dosage is 5,000 milligrams daily. What this does, is it pushes the gut to produce and repair the cells that create mucous.
Castor oil taken as an anti-inflammatory may help with the pain and swelling, but he also needs to be checked, screened, and have a blood work-up done testing for celiacs disease. Make sure that he does not have issues with gluten, because if he does, that could be the source of the inflammatory bowel disease.