My Father Has Been Taking Pantoprazole For A Month And

my father has been taking pantoprazole for a month and just had his prescription refilled. My concern is that he is tired, doesn't feel well, has dizziness and seems to be nauseous a lot. He is very very lethargic. Should he stop taking it to see if he returns to his old self. He was diagnosed with a peptic ulcer is the reason he is on it.