I have tried a bunch of those animal dewormners and think I also tried pyrantel but it was a while ago though. It seems to me a little bit too simplifying to say that one drug will kill all roundworms, especially the claim that it will immediately kill Ascaris which can be very large and is also a darn good survivor. I'm very sceptical to this claim, in that case we wouldn't need this forum anymore, if it was true I mean, but pyrantel is used a lot on horses and cats and is one of the cheapest drugs there is so worth a try though.