None of mine have ever been able to cope with Drontal. They would eat the tablet, but throw up a few hours later, so I stopped using it and now use either Panacur Granules or Milbemax with no problems.
It's probably worth phoning your vet tomorrow and explaining the circumstances and get advice if it's OK to use a different wormer so soon after the Drontal. My 4 month old puppy is fine on Milbemax.