Gus was a very tense boy. The smallest event would send him over the edge, to the point where he was under the bed, trembling badly. Given the choice to give Gus a medication "as needed," versus a medication given on a daily basis that would be "therapeutic" in his system, I chose the Clomicalm. His daily quality of life is vastly improved. While he's much less stressed, it hasn't changed his personality; it just made his demeanor such that he can deal with life's issues (knock on the door, an imagined sound outside so much better.
Clomicalm is a big help if your dog has separation anxiety. My black lab, Ninja, howls when I leave for work, pees on my rug, shreds my clothes, and otherwise trashes my apartment. From the very first dose, this helped like 75%. Now we are using techniques found on the ASPCA website and Ninja is about 90% better after two months.