A few years ago there was an injection for heartworm. I think if I remember right they dog got a shot once for the whole season and no more monthly pills.
I useds it on all 4 of my yorks and never had a problem. They took it off the market because dogs were dying and having other serious medical reactions from it.
I was so lucky that my dogs were ok with it. I am always afraid to try new things till they are on the market for a while. Why don't they test these things better before they allow us to use them on our beloved pets???
Sue & Cricket
