A very potent stimulant, usually used for either ADHD treatment in young adults, or for narcolepsy/excessive sleep, as well as weight loss. Highly addictive and often abused, particularly among the teenage and college set, dexedrine is a popular last-minute study aid, to help speed up cramming and increase focus.
The night before the big test, Jeff was off snorting coke, as Josh was popping dexedrine. Josh found the pills very effective, and thus, began to snort them, feeling jacked and high. "Oh man," he said, "I'm fiending for more dex," as he ran out of his supply, still hours before the exam. "Maybe Jeff still has some yay."