Pre and probiotics

My 89yo dad has a lot of problems with his tummy specifically bowels. He tends to be all or nothing ATM and both seem to mess with his madopar and therefore PD symptoms. He takes a plethora of other drugs which I wonder maybe be upsetting gut health. I wondered if I should try pre and probiotics to help get his tum in order. Appreciate hearing others experiences. I don’t want to introduce anything that makes life worse for him. I did search the forum but posts were pretty old.