It's for a widely used central nervous system stimulant called caffeine.

它是一种广泛使用的中枢神经系统兴奋剂，叫做咖啡因。

Caffeine is a central nervous system stimulant and as it spreads throughout the body, it boosts production of certain chemicals in the brain, making Craig more alert and energized.

咖啡因是一种中枢神经系统兴奋剂， 当它扩散到全身时，它会促进大脑中某些化学物质的产生， 使克雷格更加机敏和充满活力。