Originally Posted by Snooky

If you really mean "treatment" for a dog that has heartworms, go to the vet.
If you are talking prevention, Ivermection injectable cattle wormer. Give orally at 1/10 CC per 10# of body weight once per month.
Check the active ingrediant in Heart Guard, I think it is still Ivermection. Much more expensive than the Ivermec but no better.
DO NOT give to dogs with collie blood as it will kill them.