a tablet of dextroamphetamine, a stimulant drug (from Dexedrine, the brand under which it was marketed)
Dexies have a high potential for abuse. (example of dexie)
Short for Dextroamphetamine (Trademark name 'Dexedrine' and 'DextroStat'), the d-isomer of amphetamine, which is twice as strong as racemic amphetamine and l-amphetamine (as found in Adderall). A CNS stimulant used in the treatment of ADHD and narcolepsy. Used recreationally in high doses as a potent stimulant.
Yelena was so spun on dexies, she danced for 6 hours straight before she crashed violently into a languid stupor.
Similar to speed(drug) see "Requium for a dream" for more info
She took two dexies to stay energised