Training!! I would suggested to stay away from medicine, it's only a temporary fix, and costly one too...medicating a pet is not a solution....
Have you begun obedience training, that should make a signifcant change in attitude. I found that my puppy would try to get squirrels and such, we began with a "leave it" command indoors, and then graduated to outdoors.
An excellent book for getting a grasp on training is "Good Owners, Great Dogs"
http://www.chapters.indigo.ca/item.a...39618850531102
I hope that link worked...but I recommend you look into it and keep your pup on a lead...hope that helps...