A slang term for Dexedrine, a powerful stimulant, used for the treatment of ADHD. Dexedrine is also used by the military as a "go-pill" and is given to fighter pilots to stay alert during missions. Nicknamed dexy, it gets its name from the 80's band Dexys Midnight Runners.
"Hey, did you pick up anymore Midnight Runners?"
"Man, I just ate like 4 Midnight Runners and I'm speeding balls!"