my dog used to have advocate and drontal as recomended by our vet.
now he has just strong hold, apparently the only one that drontal does is heart worm which is not present in this countryso dog only really needs it if travelling abroad, and tape worm which humans can only catch if you eat a mouse (which i am not plannign in doing)
i have found since changing my dog has put a bit more weight on in a good way.
also the last time he had drontal he was violently sick (11 or 12 times covering my kitchen )