
I seriously doubt any issues to pups from panacur.
I have used it for 6 generations, and had the odd small pup but mostly pups average or large for their breed.
It is more likely that there were issues in the pregnancy that caused the rest of the litter to be lost and the surviving two were the lucky ones.
There could have been a low level of the hormones that maintain pregnancy, or more likely poor placentas.
My Lexi missed in October, but on palpation there was just one bead detected, but all early signs of pregnancy disappeared by 6 weeks. I suspect her hormones were not quite in harmony, as the during the season/mat9ing the dog and she were both a bit 'Oh well lets do it then', normally my girl is very rampant as is her suitor.