Excellent info, must ask my vet for this one.
They are currently recommending Advantage and Drontal to cover fleas and worms - I think it is over medicating as Advantage covers fleas, and some worms including heartworm, but not all worms. Drontal covers the ones that Advantage doesn't, but there is a lot of overlap and I'm not happy about that.
Instead, milbemax and Billy No Mates, I think!