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Caffeine Chapter 12

Caffeine Chapter 12. Lindsay Screws & Kaitlyn Dalecky. Caffeine. Usually consumed for its stimulant effects (mice/rats ) low doses  stimulant effects; high doses reversed, reduced activity

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Caffeine Chapter 12

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  1. CaffeineChapter 12 Lindsay Screws & KaitlynDalecky

  2. Caffeine • Usually consumed for its stimulant effects • (mice/rats ) low doses  stimulant effects; high doses reversed, reduced activity • (humans) low doses  stimulating and fatigue-reducing effects; high doses  feelings of tension/anxiety • Principal physcoactive ingredient in coffee • Coffea arabica • Most widely used drug worldwide • 80-90% adults • Average = 200-400 mg/day

  3. Typical Caffeine Content of Common Food Items and Drugs Brewed coffee 74-83 mg/5 oz. cup Decaffeinated coffee 2-3 mg/5 oz. cup Tea 24-30 mg/5 oz. cup Regular/diet colas 26-58 mg/12 oz. serving Milk/sweet chocolate 6-20 mg/oz. Excedrin 64.8 mg/tablet No Doz 100mg/tablet

  4. Caffeine: Pharmacology • Theophylline • Normally consumed p.o. (drank) • Completely absorbed from the GI tract = 30-60 min • Absorption begins in stomach but takes place mainly w/in the small intestine • Half-life = varies from person to person • Average = about 4 hours • Converted to metabolites by the liver • 95% eliminated through urine, 2-5% through feces, the rest through other bodily fluids (saliva) • 1-2% excreted unchanged

  5. Theophylline • Very similar actions of caffeine • Three effects: bronchodilation, heart and CNS stimulation • Antiasthmatic treatment • Devoted to synthesizing safer asthma medicine • Sleep apnea • Can be taken p.o. or rectal and injectable form

  6. Tolerance, Dependence, and Withdrawal • High caffeine consumption  tolerance to cardiovascular and respiratory effects, decreased noticeable effects • Low caffeine consumption  little tolerance, more noticeable effects

  7. Withdrawal Symptoms • Symptoms can occur in individuals who consume as little as 100 mg/day • symptoms = headache, lethargy or fatigue • Means dependency • Lasts for a few days, then dissipate • Begins at 18th hr of abstinence • Positive correlation between strength of dependency and severity of withdrawal symptoms

  8. Side Effects • Little evidence to link w/ serious disease • Possibly raises cholesterol levels & BP • Directly related to fibrocystic breast disease • Can go away w/ the absence of usage • Heartburn • Interaction with alcohol • Just as drunk, but more aroused • Not recommended for pregnant women, light sleepers, very young/old, and cardiac patients

  9. Mechanisms of Action • Does not directly influence catecholamine systems • Blocks GABAA –R, stimulates Ca2+ w/in cells  high/toxic doses • Blocks A1 and A2A –R (adenosine)  low doses • Adenosine = part of ATP (energy) • In brain, also acts as a NT • One explanation why first cup of coffee in the morning wakes some people up; refreshes a worker after post-lunch drowsiness; keeps a non-tolerant individual up at night if consumes late-night coffee

  10. Caffeine Abuse • Caffeinism • Restlessness, nervousness, insomnia, physiological disturbances (tachycardia) • Difficult to distinguish from anxiety disorder • Individuals may experience strong withdrawal symptoms and cravings if attempt to stop usage • Has characteristics of an abused substance but usually not compulsive and doesn’t affect daily function • RFT of caffeine not due to drug=induced euphoria like those of other abused drugs

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