I'd ditch the Comfortis. It's not a great drug in a lot of cases anyway. Spot on product is fine as long as it's one that vets sell (Advantage, Frontline). Some are losing effectiveness. All you can do is try. If there is a flea issue presently, make sure to use a growth regular with the adulticide (Frontline Plus and not just Frontline or Advantage II instead of just Advanage, or Advantage and Program (but Program is a pill)). Some people have success with just the adulticides and others don't.
I would get the pilling situation under control though because there will be a day that your pups will have to have pills (maybe even daily). Can you give it the same way you give heartworm pills?
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