milbemax covers a broader spectrum of worms than drontal and is the best wormer on the market, iv used panacur and iv known it to make pups sick its the same with the cheap wormers ie johnsons, shirleys etc. drontal is a decent wormer but working dogs need something to do a proper job considering some of the places they go and milbemax covers them all. But its better to worm than not to whatever you use. worm pups should be wormed @ 2, 4, 6, 8,10 & 12wks then every month untill 6months then 2-3 times per year this is especially important with bitches intended to be bred from.