Nicole, are you sure there are no fleas around? Is your dog being treated with a flea preventive like frontline or a similar product? Sometimes fleas may be present in low numbers and not readily apparent.
You might also want to ask your vet about other remedies. I believe Panacur controls at least some types of tapeworms (Taenia tapeworms).
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."