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Common psychostimulants: Caffeine and nicotine

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

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  1. Common psychostimulants: Caffeine and nicotine Sources Pharmacokinetics Pharmacodynamics Side effects

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. More side effects • High toxicity from tobacco and administration routes • Damages unborn children • Environmental pollution and second- • hand smoke

  13. 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

  14. 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.

  15. 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

  16. 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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