Over the years I have met several breeders that use it for heart worm preventative. Here is an article I found on the internet that explains how one person uses it.
CANINE HEARTWORMS AND INEXPENSIVE PREVENTION
There are many products on the market that are made for horses or fish (antibiotics) that can be safely used on dogs if you know the proper dosages. I would really have to research the product before I would try it on any of my dogs.