This potion is made from the distilled essence of pure sugar. Only the strongest metabolisms are able to support such an eightened speed but, luckily, earth ponies are quite endurant. Also, huge amounts of sugar are required for the body to maintain that hyperhyperactive state. That's why Pinkie's diet consists almost exclusively of sugary things. With enough repetition, even the tastiest things turn bland. And that's why she uses hot sauce.