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10/15/2014 Caffeine is the Most Widely Used Psychoactive Drug Worldwide Tea is the most widely consumed beverage in the world Tea is the most widely consumed beverage in the world. USA – 80% of adults consume caffeine. Caffeine is the Most Widely Used Psychoactive Drug Worldwide FDA regulates caffeine added to sodas but not all energy drinks – “nutritional supplements”. Tea has more caffeine by dry caffeine by dry weight than coffee though brewed weaker. Espresso drinks generally have less caffeine than drip coffee. 1 10/15/2014 Caffeine Pharmacokinetics Absorption Rapid and high – 99% bioavailability Significant blood levels reached within 15‐20 minutes 45 minutes – complete absorption Caffeine half‐life ranges from 3‐7 hours Caffeine Pharmacokinetics Distribution Caffeine is soluble in water and oil and distributes throughout the human body. Caffeine readily crosses the BBB and placenta. 2 10/15/2014 Caffeine Pharmacokinetics Elimination Only 2‐3% of unchanged caffeine is eliminated in the urine. Kidneys excrete the active metabolites. Caffeine is Metabolized by CYP1A2 theophylline (12%) paraxanthine (84%) caffeine theobromine (4%) Metabolites are also stimulants though less active than caffeine. 3 10/15/2014 Caffeine Metabolism Affected by Other Drugs Drugs that prolong half‐life of caffeine (CYP1A2 inhibitors) • Alcohol • Oral contraceptives • Pregnancy hormones • Some SSRIs (Prozac®, Luvox®) Drugs that shorten half‐life of caffeine (CYP1A2 inducers) • Cigarettes* * Half‐life increases upon termination of smoking Caffeine Mechanism of Action Caffeine is an antagonist of the adenosine receptors. Adenosine is a neuromodulator that influences release of other neurotransmitters, promoting sleep and suppressing arousal. adenosine caffeine Inhibition of adenosine actions results in increased wakefulness and alertness. 4 10/15/2014 Caffeine Pharmacological Effects – Positive • Constriction of cerebral blood vessels – reduced pressure in brain providing headache relief • Dilation of coronary arteries – associated with lowered risk for coronary heart disease • Improved glucose metabolism, insulin secretion, and reduced risk for type 2 diabetes • Reduced risk for cancers including: endometrial, prostate, head and neck, basal cell carcinoma • Protection against liver disease and gout •Bronchial relaxation (antiasthmatic) Caffeine and CNS Health Protective effect against Parkinson’s disease (PD). g ( ) Coffee and tea both beneficial, though decaffeinated coffee ineffective. ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Decreased risk of Alzheimer’s disease (AD). Increase in granulocyte colony secreting factor (GCSF). 5 10/15/2014 Negative Effects of Caffeine at High Doses Lethal dose is about 10 grams. Heavy doses ( > 1 g) can lead to caffeineism: • Agitation • Anxiety • Tremors • Rapid breathing • Insomnia • Mood changes Mood changes • Tachycardia (rapid heartbeat) • Cardiac arrhythmias (irregular heartbeat) • Hypertension • GI disturbances http://kova107.deviantart.com/art/tweek‐caffeinism‐156037714 Reproductive Effects Limited and controversial data suggest potential effects of caffeine on fetuses include: Limited and controversial data suggest potential effects of caffeine on fetuses include: • Decreased birth weight • Slight increase in risk of miscarriage with very large doses Recommended intake less than 200 300 mg Recommended intake less than 200 – 300 mg 6 10/15/2014 Caffeine and Alcohol Caffeine can reduce some effects of alcohol including: • Motor impairment • Sedation • Hangover symptoms http://www.fda.gov/ForConsumers/C onsumerUpdates/ucm233987.htm Caffeine Tolerance and Dependence Tolerance and dependence can form rapidly even with low doses (100 mg/day). Withdrawal symptoms: • Headache • Drowsiness • Fatigue • Negative mood state “Alertness” felt by frequent caffeine users may be due to reversal of acute withdrawal effects. “Normalcy” state 7