They're stimulants, that act to activate the sympathetic nervous system, generating a sense of euphoria and increasing the alertness as well as aggression. They become abused with time, since they're sympathomimetics and cause the body in time to stop producing the natural sympathetic neurotransmitters, and they're currently on the World's Doping Agency Prohibited List
am·phet·a·mine
n.
1. A colorless, volatile liquid, C9H13N, used as a central nervous system stimulant in the treatment of certain conditions, such as attention deficit hyperactivity disorder, depression, and narcolepsy, and abused illegally as a stimulant.
2. A derivative of amphetamine, such as dextroamphetamine or a phosphate or sulfate of amphetamine.
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