I use Klonopin now. I don't have anxiety from running, but I didn't have a good way of handling stress at work and that led me to the anxiety. Even though work is the cause of my anxiety, it is most visible during my running performance, especially training. At its worst, I can't run as fast as I can walk. Ordinarily a sub 15 and sub 31 guy.
I used Buspar (Buspirone) for one day 30 months ago and I think a lot of my physical sensitivity (I have tourettes-like symptoms around loud music, bright lights, and cold weather) It was way worse the first day I used it, but its still a problem now. My doctor swears that wasn't the cause, but spending a month not sure when you'll be able to stand upright was the worst experience of my life.
Counseling is probably best, but there are a lot of shitty counselors out there. I don't see one, but I am probably being too stubborn.
I also don't take the night or morning of a race. I can focus on the race and not worry about the rest of life during a race, so no need. I only say this because maybe running isn't what is causing the anxiety.