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How is methamphetamine different
from other stimulants, such as cocaine?
Methamphetamine is
structurally similar to
amphetamine and the
neurotransmitter dopamine, but it is quite different from cocaine.
Although these stimulants have
similar behavioral and physiological
effects, there are some major
differences in the basic mechanisms
of how they work. In contrast
to cocaine, which is quickly
removed and almost completely
metabolized in the body,
methamphetamine has a much
longer duration of action and a
larger percentage of the drug
remains unchanged in the body.
This results in methamphetamine
being present in the brain longer,
which ultimately leads to prolonged
stimulant effects. And
although both methamphetamine
and cocaine increase levels of
the brain chemical dopamine,
animal studies reveal much
higher levels of dopamine
following administration of
methamphetamine due to the
different mechanisms of action
within nerve cells in response to
these drugs. Cocaine prolongs
dopamine actions in the brain
by blocking dopamine re-uptake.
While at low doses, methamphetamine
blocks dopamine
re-uptake, methamphetamine
also increases the release of
dopamine, leading to much
higher concentrations in the
synapse, which can be toxic to
nerve terminals.
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Methamphetamine |
vs. |
Cocaine |
Man-made
Smoking produces a high that lasts 8-24 hours
50% of the drug is removed from the body in 12 hours
Limited medical use
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Plant-derived
Smoking produces a high that lasts 20-30 minutes
50% of the drug is removed from the body in 1 hour
Used as a local anesthetic in some surgical procedures
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What are the long-term effects of methamphetamine abuse?
Long-term methamphetamine
abuse has many negative
consequences, including
addiction. Addiction is a chronic,
relapsing disease, characterized
by compulsive drug seeking and
use, accompanied by functional
and molecular changes in the
brain. In addition to being
addicted to methamphetamine,
chronic abusers exhibit symptoms
that can include anxiety, confusion,
insomnia, mood disturbances,
and violent behavior.
They also can display a number
of psychotic features, including
paranoia, visual and auditory
hallucinations, and delusions
(for example, the sensation of
insects creeping under the skin).
Psychotic symptoms can sometimes
last for months or years
after methamphetamine abuse
has ceased, and stress has been
shown to precipitate spontaneous
recurrence of methamphetamine
psychosis in formerly psychotic
methamphetamine abusers.
With chronic abuse, tolerance
to methamphetamine's pleasurable
effects can develop. In an
effort to intensify the desired
effects, abusers may take higher
doses of the drug, take it more
frequently, or change their
method of drug intake. Withdrawal
from methamphetamine
occurs when a chronic abuser
stops taking the drug; symptoms
of withdrawal include depression,
anxiety, fatigue, and an
intense craving for the drug.
Chronic methamphetamine
abuse also significantly changes
the brain. Specifically, brain
imaging studies have demonstrated
alterations in the activity
of the dopamine system that are
associated with reduced motor
speed and impaired verbal
learning. Recent studies in
chronic methamphetamine abusers have also revealed
severe structural and functional
changes in areas of the brain
associated with emotion and
memory, which may account
for many of the emotional and
cognitive problems observed in
chronic methamphetamine
abusers.
Fortunately, some of the
effects of chronic methamphetamine
abuse appear to be, at
least partially, reversible. A
recent neuroimaging study
showed recovery in some brain
regions following prolonged
abstinence (2 years, but not 6
months). This was associated
with improved performance on
motor and verbal memory tests.
However, function in other
brain regions did not display
recovery even after 2 years of
abstinence, indicating that some
methamphetamine-induced
changes are very long-lasting.
Moreover, the increased risk of
stroke from the abuse of
methamphetamine can lead to
irreversible damage to the brain.
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