He may not have the enzymes to utilize the Glucosamine like he did before the gastric tube.
Glucosamine Hcl is cheaper and it is harder
for the body to utilize than the higher quality Glucosamine sulfate.
With that being said, Glucosamine sulfate is commonly use in people who have GI problems because it helps to protect the mucus membranes and heal injuried tissue. It is a very important supplement in IBS, Chrones disease, ulcers etc.,
I feel really bad for you and your dad.