Transcript Chapter 8—Caffeine & Nicotine

Chapter 8—Caffeine & Nicotine
Robert M. Julien
Presentation By:
Tamyra Frazier & Sarah Massamore
Differentiate CNS Stimulant Actions of Caffeine
From Those of Amphetamine & Cocaine.
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Unlike the actions of cocaine & amphetamine,
caffeine does not induce a release of dopamine in
the nucleus accumbens; it leads to a release of
dopamine in the prefrontal cortex, which is
consistent with caffeine reinforcing properties.
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It appears that although caffeine fulfills some of the
criteria for drug dependence & shares with
amphetamines & cocaine a certain specificity of
action on the cerebral dopaminergic system, it
does not act on the dopaminergic structures related
to reward, motivation, & addiction.
Mechanism of Action--Caffeine
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4 different adenosine receptors (A1, A2A, A2B, A3) exist
in humans, & caffeine is most potent in blocking A1 &
A2A.
The positive stimulatory effects appear in large
measure to be due to blockade of A2A receptors that
stimulate GABAergic neurons of inhibitory pathways
to the dopaminergic reward system of the striatum.
Caffeine as a competitive antagonist at adenosine
receptors, may produce its behavioral effects by
removing the negative modulatory effects of
adenosine from dopamine receptors, thus stimulating
dopaminergic activity.
Panic Attacks & Caffeine
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The usually ingested doses of
caffeine do not induce panic attacks
in normal individuals. However, in
people predisposed to panic
disorders, the peripheral & the CNS
effects of caffeine are exaggerated.
Effects of Caffeine in the
Cardiovascular System
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Slight stimulant action on the heart.
Increases both cardiac contractility
(workload of the heart) & cardiac output.
 Raises blood pressure in adults prone to
hypertension. Dilates the coronary
arteries, providing more oxygen to the
harder working heart.
 Constricts the cerebral blood vessels,
decreasing blood flow to the brain by 30%
(migraines).
Evidence for & Against Caffeine
Use by Pregnant or Nursing Women
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Safety during pregnancy is unresolved.
Caffeine in breast milk equals or exceeds level that exists in
the mother’s plasma
Heavy consumption (6+ cups) is associated with an
increased risk of spontaneous abortion but moderate
consumption does not further increase the risk.
Does not appear caffeine is a teratogen, & it does not
appear to affect the course or normal labor & delivery.
Relatively safe in moderate doses. Higher levels=increased
incidence of intrauterine growth. Later study showed low
doses in 1st trimester increased risk of intrauterine growth
retardation; high consumption, even in month before
pregnancy, nearly doubled the risk of spontaneous
abortion.
Smoking Statistics

450,000 smokers die annually: 115K (lung cancer), 30K (cancer of
other organs), 200K (heart & vascular diseases)
 Life span shortened by 14 minutes for every cigarette smoked. 2
packs/day*20 years= 8 years of life lost
 Smoking, the greatest public health hazard, is ironically the most
preventable cause of premature death, illness, & disability
 50 million+ people (1/5) alive today will die prematurely from
effects of smoking
 9 million suffer from cigarette-induced bronchitis & emphysema.
70% of pulmonary diseases & deaths, 57K emphysema deaths are
tobacco related
 Of all cancer deaths in the US, 30% (154K) would be prevented if
no one smoked.
Nicotine As an Antidepressant
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Several reports note an antidepressant effect of nicotine as
well as the comorbidity of depression with cigarette use.
Subjects with depression had odds of nicotine dependence
that were more than 4.5x the odds for those w/o
depression. This begins as early as age 16.
In nonsmokers, transdermal nicotine patches produced
improvement in depression. Researchers think the high rate
of smoking among depressed individuals may represent an
attempt at self-medication to assist in dealing with
symptoms.
Addictive or Habit Forming?
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Nicotine clearly induces both physiological &
psychological dependence in a majority of smokers.
In 1988, the surgeon general concluded that:
– Cigarettes & other forms of tobacco are addicting.
– Nicotine is the addictive drug in tobacco.
– The pharmacological & behavioral processes that determine
tobacco addiction are similar to heroin & cocaine.
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In total, the evidence clearly identifies nicotine as a
powerful drug of addiction, comparable to heroin,
cocaine, & alcohol.
Nicotine Replacement Devices
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Nicotine patches, nicotine gum, inhalers, etc.
Experts identified nicotine replacement therapies as
the only pharmacotherapy showed to be effective as
an aid to smoking cessation.
All methods of nicotine replacement appear to be
equally efficacious, approximately doubling the
quitting rate of smokers attempting to quit w/o
assistance.
The limitations are in health care workers who fail to
recommend or monitor their use during cessation.
Nicotine Therapies &
Antidepressants
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Efficacy of Nortriptyline is reported but supra-additive
effect of the drug plus cognitive-behavioral therapy.
• The antidepressant Bupropion doubled quitting rates.
• Combination of Bupropion & nicotine patch only
slightly improved the results over use of only
Bupropion.
• Bupropion is equally effective whether the smoker is
or is not clinically depressed, suggesting that
Bupropion’s efficacy is not solely due to its
antidepressant effect.