Hopefully he'll be OK. If a vet said pred then follow it but make sure to keep an eye on him. Make sure he's not throwing up or coughing up a lot of mucus. Dogs can eat stuff that won't pass and could cause issues like this. Deep(broad/large) chested dogs can also come up with an issue of where their stomach can actually flip around and cause issues like but it's not very common but is very serious if it happens. Just keep an eye on him. If he ends up actually throwing up the pred and can't keep anything down then get him to a vet quick.