Common psychostimulants caffeine and nicotine
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Common psychostimulants: Caffeine and nicotine. Sources Pharmacokinetics Pharmacodynamics Side effects. Caffeine. Most popular drug in the world “Caffeine is useless since it serveth neither Nourishment nor Debauchery.” --Anonymous, 1650. Xanthine derivatives or methylxanthines:.

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Common psychostimulants caffeine and nicotine l.jpg

Common psychostimulants: Caffeine and nicotine

Sources

Pharmacokinetics

Pharmacodynamics

Side effects


Caffeine l.jpg
Caffeine

  • Most popular drug in the world

  • “Caffeine is useless since it serveth neither Nourishment nor Debauchery.” --Anonymous, 1650

Xanthine derivatives or methylxanthines:

  • Caffeine

  • Theophylline

  • Theobromine


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Sources of caffeine

  • Plants of 28 genera in 17 families

  • Most common sources are coffee, tea, chocolate, and kola

  • Coffea arabica and Coffea robusta

  • Camellia sinensis: Green, black, and oolong

  • Theobroma cacao

  • Kola/cola

  • Ilex paraguayensis, Ilex vomitoria


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Pharmacokinetics

  • Oral administration

    • Beverages: Coffee, tea, cocoa, chocolate milk, cola (fortified)

    • Chocolate

    • OTC preparations

      • Stimulants

      • Pain-killers (caffeine synergizes acetylsalicylic acid)

      • Diuretics and cold preparations

  • Elimination half-life ranges from 3 to 10 hrs

    • Longer late in pregnancy, in utero, elderly

    • Concentrated in breast milk

    • Shorter in smokers


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Pharmacodynamics: Effects

  • Cortex at normal doses (100-200 mg):

    • Rewarding effect: Feel competent

    • Alertness, sustained attention, faster thought

    • Reduced fatigue, lower need for sleep

    • Fine motor coordination, timing accuracy, and arithmetic may be impaired

  • Heavy dosing (1.5 grams a day) may produce agitation, anxiety, tremors, panting, and insomnia


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More effects of caffeine

  • Spinal cord stimulated at toxic doses (2 - 5 grams); cardiac arrhythmias at 10 - 20 grams

  • Dilates coronary arteries; constricts cerebral arteries

  • Bronchodilation


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Pharmacodynamics: Mechanisms

  • Mediated by blockade of adenosine receptor

    • A normal dose blockades 50% of receptors

  • Adenosine is not a neurotransmitter but a neuromodulator or autacoid.

  • Adenosine, and thus caffeine, act on NE, DA, ACh , glutamate, and GABA

  • DA activity is especially increased, but not in the nucleus accumbens


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Side effects of caffeine

  • Caffeine-induced disorders from DSM-IV

  • Conflicting data on reproductive effects

    • May slow growth in utero, especially high dose

    • Caffeine may be harmful prior to conception

    • May increase the risk of spontaneous abortion

  • Withdrawal effects due to increased adenosine receptor density and thus increased adenosine sensitivity


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Nicotine

  • Source: Tobacco

  • Administration:

    • Inhalation: Smoking tobacco tars

    • Intranasally: Snuff

    • Oral/buccal: Chewing tobacco

    • Oral/gastrointestinal: Nicotine gum

    • Transcutaneous: Patches

  • All produce comparable blood levels


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Pharmacokinetics and pharmacodynamics

  • Distributes rapidly to all body compartments, analogous to smoke

  • Stimulates nicotinic ACh receptors

    • Enhances cortical activity, including attention and memory

    • Activates neuromuscular junction and ANS

  • Stimulates DA pathways from VTA to nucleus accumbens


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Side effects

  • Vomiting and nausea tolerate rapidly

  • Otherwise, little tolerance but dramatic dependence

  • Stimulates hypothalamic ADH and consequent fluid retention

  • Reduces afferent input from muscles, lowering muscle tone: Relaxation and flabbiness


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More side effects

  • High toxicity from tobacco and administration routes

  • Damages unborn children

  • Environmental pollution and second-

  • hand smoke


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Therapies

  • Standard protocol (Julien, 1995):

    • 1. Withdrawal

    • 2. Diagnosis

    • 3. Treat coexisting conditions

    • 4. Reduce drug craving

    • 5. Prevent relapse

  • Divide and conquer: Nicotine replacement and reduction; clonidine, buspirone, or antidepressants to reduce craving

  • American Lung Association plan


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  • The Great American Smoke-out Day

    • Third Thursday in November

    • Began in Randolph, MA in 1971

    • Went national in 1977

    • More Americans quit smoking this day than any other

  • Quitting smoking may be a learned behavior: Repeated failure may lead to success.


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Cell product exports

  • Neurotransmitters

    • Effects restricted to cells at synapse

  • Neuromodulators or autacoids

    • Effects on a few cells or an area of cells

  • Hormones and neurohormones

    • Effects on area served by circulation system

  • Pheromones

    • Effects on other organisms


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How much caffeine?

5oz 5oz 5oz 1oz 1oz 12oz Tab- Anal- Diur-

Coffee Tea Cocoa Choc. C.Milk Cola lets gesics etics


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