Losec will not stop him from throwing up at all. It merely stops the body from developing stomach acid, so when they do throw up it doesn't hurt as there's no acid there. The vomitting will continue while on Losec, it only helps with the pain.

I was more thinking that if he is throwing up after having the losec, he is throwing up the losec as well, so, therefore, not getting as much in IYKWIM?