Our 8 week old pup has liquid stools 5 days after worming?

Frank is er and came with tapeworm. Vet gave him drontal on Tuesday along with flea treatment. Frank is fine in himself, very happy and bouncy but does have liquid stools, I expected this but not 5 days later. He eats ped chum puppy complete. Can I give him chicken and rice to try to settle his tum? How long should loose stools last after worming? Any suggestions would be great!