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Caffeine is the most widely used
psychoactive substance in the world. It was first isolated from
coffee in 1820. Although caffeine is considered a weak Central
Nervous System (CNS) stimulant, people should be aware that it
can be a dependence-producing drug and that there are harms
associated with its use.
Caffeine belongs to a family of
drugs known as xanthine stimulants or methylxanthines. The
methylxanthines are found naturally in a number of plants but
the most common sources are coffee, tea and chocolate. Caffeine
is also added to a number of cola beverages as well as to many
prescription and over-the counter medications. It is added to
these products for its CNS stimulating effects, for relief of
vascular headaches, or to enhance analgesia.
Below is some common sources of
caffeine and their approximate caffeine content in milligrams.
Amounts given for beverages are per
5 oz. cup serving and pills are per tablet.
The exact mechanism behind the
stimulating effects of caffeine on the central nervous system is
not fully understood. These effects can vary among individuals,
with the amount ingested, and with the regularity of
consumption.
Consuming 100 to 200 mg of caffeine
(roughly the amount in 1 to 2 cups of coffee) increases
alertness, heightens vigilance, maintains the capacity to
perform complex functions, and decreases fatigue by stimulating
areas of the brain.
Higher doses (12 to 15 cups of
coffee) can produce anxiety and tremors.
Caffeine ingestion 30 to 60 minutes
before bedtime can delay sleep, decrease total sleep time, and
decrease sleep quality. The degree of impact on sleep is usually
dependent on regularity of use; less frequent use can produce a
greater impact.
Smokers eliminate caffeine twice as
quickly as non-smokers; pregnant women eliminate caffeine more
slowly than non-pregnant women.
Consuming 3 to 10 grams of caffeine
(equivalent to 30-100 cups of coffee) may cause vomiting,
convulsions, and irregular heartbeat and may result in death
from convulsions and respiratory depression.
Factors
which can influence the answer to this question include:
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If
a person is a nervous, easily stressed individual or has
heart problems or migraines, more than 150 mg of caffeine
per day may be too much.
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If
a person has mental health problems, a high intake of
caffeine may increase symptoms of the illness or may
interact with prescribed psychiatric medications by
increasing or decreasing their effects.
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Small amounts of caffeine have a greater effect on children
than on adults because of body size. It is wise to be aware
of how much caffeine children consume in chocolate products,
soft drinks, and medications.
Although caffeine is rarely
considered a drug of abuse, it produces mild psychological and
physical dependence. Regular use of more than 350 mg of caffeine
a day produces physical dependence. Withdrawal symptoms may
include nausea, tiredness, headache, and constipation. Other
symptoms may consist of impaired concentration, decreased
motivation and irritability. These symptoms typically appear
12-24 hours after the last use, peak in 24-48 hours, and may
last a week.
Drug Dependency Services, Central
Region, 1999
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