The vet told me our cat didn't need anti-flea med if he didn't go outside (my cat has never been outside). But the cat kept scratching until he developed the flea allergy dermatitis, and went wild, and bit himself, whenever I touched his back. Then the vet said the cat did have fleas, and prescribed Advantage. It seems to work initially. But I am concerned about the fact that it doesnt seem to be effective for the entire month. The instructions say not to use it more than once a week. Does this mean I should use it every 2 or 3 weeks? I also wonder about the alternative packaging, with the cats sitting upright, with more purple or orange on the front of the package; is this newer packaging? which could possibly mean the the packaging shown here is old product.