Uhmm hi. will mixing 4-8mg of Ondansetron (Zofran) have any major effects with 25-37mg of Promethazine (Phenergan)? (I'm honestly not sure if I made this post before)

I heard about the moderate breathing problems associated with mixing the two, and since I have been having minor breathing problems, mixing wouldn't be the best idea. How much time should pass before I can switch?

My stomach is burning, and the upset if from acid -- that I'm sure of -- but I don't know. Just feeding my anxiety I guess.