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Stimulants
Any drug that excites any bodily
function, but more specifically those that stimulate the brain and central
nervous system. Stimulants induce alertness, elevated mood, wakefulness,
increased speech and motor activity and decrease appetite. Their therapeutic use
is limited, but their mood-elevating effects make some of them potent drugs of
abuse.
The major stimulant drugs are amphetamines and related compounds,
methylxanthines (methylated purines), cocaine, and nicotine.
Amphetamines achieve their
effect by increasing the amount and activity of the neurotransmitter
norepinephrine (noradrenaline) within the brain. They facilitate the release of
norepinephrine by nerve cells and interfere with the cells' reuptake and
breakdown of the chemical, thereby increasing its availability within the brain.
The most commonly used amphetamines are methamphetamine (Methedrine),
amphetamine sulfate (Benzedrine), and dextroamphetamine sulfate (Dexedrine).
Amphetamines were first used in the 1930s to treat narcolepsy and subsequently
became prescribed for obesity and fatigue.
Their heavy or prolonged use
causes irritability, restlessness, hyperactivity, anxiety, excessive speech, and
rapid mood swings. Still higher doses or chronic use can cause agitation,
tremor, confusion, and, in the most serious cases, a state resembling paranoid
schizophrenia. Moreover, letdown effects of deep depression and physical
exhaustion may occur after only a single dose of moderate strength wears off.
With repeated use, tolerance develops, so that a user needs to take larger
doses, but the accompanying dependence is not strong enough to be termed a
physical addiction. Amphetamines are widely abused, in some cases by workers or
students seeking enhanced physical energy and mental acuity to fulfill demanding
tasks.
Certain drugs related to the amphetamines have the same mode of
action but are somewhat milder stimulants. Among them are phenmetrazine
(Preludin) and methylphenidate (Ritalin). The latter drug is widely used to
“slow down” hyperactive children and improve their ability to concentrate.
The methylxanthines are even milder stimulants. Unlike the
amphetamines and methylphenidate, which are synthetically manufactured, these
compounds occur naturally in various plants and have been used by humans for
many centuries. The most important of them are caffeine, theophylline, and
theobromine. The strongest is caffeine, which is the active ingredient of
coffee, tea, cola beverages, and maté. Theobromine is the active ingredient in
cocoa. Caffeine constricts blood vessels of the brain; for this reason it is
often a component of headache remedies. Theophylline is used in the treatment of
severe asthma because of its capacity for relaxing the bronchioles in the lungs.
Cocaine is one of the strongest and shortest-acting stimulants
and has a high potential for abuse owing to its euphoric and habit-forming
effects. Nicotine, the active ingredient in cigarettes and other tobacco
products, may also be regarded as a stimulant.
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