Actually, Red Dye 40 might make you go go go go go, but I’m not sure exactly how long it lasts.  I’ve never really timed Luna.  And I’m not about to give her any.  “F” that. 
When I was writing and drawing this strip, I wanted to convey 3 ideas in the dialogue…
1) It makes her run fast
2) It doesn’t last long
3) Although it appeared she was running in a straight line, she was really just running in circles.  This was to be the real joke of the strip.
Unfortunately, it was too much info.  So I opted to imply the running-in-circles through art.
Hope it was apparent enough.
John Vogel