My dogs take Interceptor once a month to prevent heartworms, and from what I understand, the other worms are taken care of by the Interceptor, also. I know that my dogs haven't had worms of any kind. Interceptor has to be prescribed by a vet, and the dogs have to be tested for heartworms first.
I also understand that Heartguard can be given to a heartworm positive dog, but I don't think it kills the other worms. I am giving it my heartworm positive dog Heartguard, and there's been no adverse reactions. The reason I'm giving it is that the Heartguard will kill new heartworms I guess when they hatch.
Alice