amphetamine
Amphetamine, any of a group of powerful stimulant drugs that act on the central nervous system (the brain and the spinal cord), increasing heart rate and blood pressure while reducing fatigue. Although amphetamines were originally prescribed to suppress appetite and to treat depression, their medical use is now restricted primarily to treating narcolepsy (sudden and uncontrollable sleep attacks) and hyperactivity. The amphetamines include drugs that are classified as amphetamines, dextroamphetamines, and methamphetamines

Amphetamines act by stimulating the release of neurotransmitters such as norepinephrine that increase brain activity and raise blood pressure. When initially taken, amphetamines produce feelings of well-being, increased competence, and alertness. High doses of amphetamines can cause tremors, sweating, heart palpitations, or anxiety. Exhaustion and depression follow when the effects of amphetamines wear off. Serious mental illness including paranoia, delusions, hallucinations, and violent behavior may occur after prolonged use. Since chronic use reduces appetite, weight loss may be drastic, resulting in a gaunt, wasted appearance. Amphetamines are commonly abused by individuals seeking mood elevation, increased alertness, or improved athletic performance. Intravenous injection of methamphetamines, for example, produces a sudden, pleasurable, euphoric feeling

Regular medical and recreational use of amphetamines can lead to greater physical tolerance of the drug, requiring progressively higher doses to achieve the same effects. Ultimately, psychological drug dependency may result, characterized by a craving for the drug and belief that one cannot function without taking it (see Drug Dependence