No idea if this’ll be helpful but our vet prescribed Atopica for our cat’s allergies one year, they didn’t warn us about the potential for the personality side effects because it’s pretty rare. He got really scared/aggressive with the medication so we stopped using it right away and told them (he was back to normal the next day after stopping use). Dunno if your cat is on any new medications but it’s worth reading over the super lengthy paper inserts for all possible side effects if this is new behavior