Zantac for newborn?

My baby randomly choked yesterday he went to the doctor and everything was fine. He was clear— my doctor said she would try Zantac but she seemed reluctant. My sis said she tried it once and it burned her babies butt.

My baby choked again today, I heard a loud noise like rumble in his tummy and then he had that scared look in his face. I think it’s a painful burp. Doctor switched him to similac alimentium recently and I’m only have trouble with it. I just want to make sure if I go on this my baby will be fine. I don’t want further discomfort.