Re: vomiting Great Dane
First as Pat suggested, you need bloodwork to rule out underlying cause. Any vet just "guessing" at pancreatitis without actually checking lab work (which could tell the vet more definitively that is or is not the issue) is not a vet I would feel confident in.
What I would be concerned about at his age and breed is: GVD or bloat/torsion. It is possible he has a mild case or even an intermitent obstruction (intermittent to mean that something is in the stomach, at times it moves and allows food to pass normally but then moves again to block the foods passage, causing them to vomit. Which in turn makes the obstruction move again and allow passage). Cancer would be another thing I would be worried about, as is kdney or liver disease - all of which can cause vomiting issues.
That does not mean this is what he has, only that these are possibilities that need to be investigated and slowly checked off as not being the issue.
So at the very least - bloodwork, including urinalysis. At the most I would do labs and contrast xrays (with a contrast dye to show the contents of the stomach in case of intermittent obstruction) An ultrasound might be a better, though more pricey option.
If after all of this has been done and he is deemed "normal or healthy", I would look at motility issues. Which is easily treated with Reglan or Metoclopramide.
Again - after everything is deemed normal - I might also gradually switch to a bland and easily digestable diet in addition to the Reglan.
As always - it is best to work alongside your vet to determine his issues. Good luck.
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