Download 10/15/2014 Caffeine is the Most Widely Used Psychoactive Drug Worldwide

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.
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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.
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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.
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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.
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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).
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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
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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
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