I have my dachshunds on heartworm medication because of the number of insects we have in my area. My vet has them on Interceptor, which seems to be a pretty good medication.
I like the fact that Interceptor takes care of not only heartworm, but also hookworm, roundworm and whipworm infestations. I also like the fact that it comes in flavor tabs, which I can give to my dogs by itself and they actually eat it without it having to be put in their food or into a pill pocket (though you can do that, too, if you want).
Interceptor is a once a month medication. I have to give it to my dogs for six months, and it comes in different strengths depending on the weight of your dog. It is also color coded for easier identification. I have one of my doxies on the medication that is for 2-10 lb. dogs. My other two doxies are a little heavier and bigger, and they are on the medication for dogs 11-25 lbs. Of course, a blood test must be done by the vet to make certain that the dog is not already infected with heartworm before treatment with this medication can begin.
Interceptor is a broad spectrum parasiticide, and I feel better knowing that my dogs are protected. I know that the medication can probably be gotten for less than $25.00 at other places, my vet is somewhat expensive. But to keep my dogs safe, it's worth it.