Familiar Stimulants: Caffeine
The most widely used “drug” in
the world !
Learning Objectives YWBAT:
-List the 3 types of methylated xanthines
and indicate common sources.
-Describe the physical and mental effects of
caffeine at ―higher‖ and ―lower‖ doses.
-Explain the stimulant action of caffeine on
the NT’s (CNS) & hormones (body).
-Explain how caffeine helps to sustain
muscular activity.
What is caffeine?
• Most ―well known‖ member of the
methyl xanthine class of stimulants
• Fairly powerful central nervous system
stimulant
• 1820 isolated from coffee
• Found in 63 plant species !!
Other members of the methyl
xanthine family of stimulants
• THEOPHYLLINE - found in tea.
The most potent methylated
xanthine. Fact: Used to Tx asthma
• THEOBROMINE - from cacao beans
Contained in chocolate. Little
stimulant effect on body or CNS.
http://www.iconbazaar.com/molecules/drugs/stimulants/theobromine.html
Cocao Beans— Theobroma cacao
Isolated chemicals:
Theobromine
Theophylline
Ethanolamine
Anandamide (~MJ)
Common uses: Chocolate & Diuretics
Kola Nut & Caffeine
• Formerly used in cola beverages
• Supplied caffeine & flavor
Kola Nuts & Caffeine
• The name for cola drinks is derived from
this plant, although the cola nut is no
longer used as an ingredient in most
commercial drinks.
• Currently many stimulant uses worldwide.
Common Caffeine Products
• Coffee
• Tea
• Cola beverages
• Chocolate
• Chocolate-flavored foods
• Prescription drugs
• OTC drugs
http://www.coffeescience.org
Caffeine doses in OTC Products
– Vivarin 200 mg
– No-Doz 200 mg
– Dexatrim 200 mg
– Excedrin 130 mg
– Tylenol 0 mg
*Caffeine increases the effectiveness of pain relievers.
Intended/ Desired Effects
• Increases neural activity;
concentration, alertness
• Postpones exhaustion
• Improves reaction times
• Performance of “simple”
mental and physical tasks
• Boosts short-term memory
• Feelings of well-being
Common Medical Uses
• Treatment of some headaches
• Tx ―unusual‖ levels of tiredness,
weakness, or drowsiness
• Breathing problems (why? how?)
• Sometimes used to stimulate
respiration in premature infants
Caffeine & NT Adenosine
• Caffeine is similar in structure to
adenosine, NT that slows CNS activity.
• The two chemicals, caffeine & adenosine,
compete for the same receptor sites.
• The more caffeine present, the less
adenosine is able to act (up to a point).
• That’s why caffeine temporarily heightens
concentration and wards off fatigue . . .
. . . But can cause a crash.
Primary CNS Action of Caffeine
• Central Nervous System
• Stimulant action
• Blocks CNS inhibitory receptors
for the NT, Adenosine
• Overall result of ―blocking
adenosine inhibitory action‖. . .
. . . is CNS stimulation !
Explain this “adenosine” thing again
• Adenosine normally slows CNS activity
• But caffeine blocks adenosine receptors.
• Bottom Line = caffeine inhibits the normal
CNS ―braking‖ effect of adenosine . . .
. . . No brakes . . .
• Result of blocking the action of adenosine
is a net increase in CNS activity.
Other Actions of Caffeine
• besides CNS stimulation . . .
• Peripheral & Autonomic Systems
• Release of hormone epinephrine
(adrenaline)* from adrenal glands
• Release of free fatty acids from
the liver (fuel for muscle activity).
Combined caffeine actions are
helpful for CNS alertness and
muscular endurance activities.
Adrenaline? or Epinephrine?
Although widely referred to as
"adrenaline" outside of the US, and the lay
public worldwide, the correct term for
this chemical in the USA is "epinephrine―.
WHY? because "adrenaline" bore too much
similarity to the Parke, Davis & Co trade
brand ―Adrenalin" (without the "e") which
was registered in the US.
Short Term Caffeine Effects
• Increased heart • Constricts brain
rate & BP blood vessels
• Increased • Dilation of heart
breathing rate blood vessels
• Increased • Increase in gastric
urinary acid production*
output/can lead • Decrease in visual
to dehydration & auditory acuity
• CNS stimulation • Sleep disturbance
*increase in gastric reflux possible
Duration of Effects
• Maximal CNS effects occur
about 30 to 60 minutes after
ingestion.
• Maximal CNS effects last about
2 hours.
• Up to 30 hours for complete
elimination from the body.
Benefits of Caffeine at ―Lower Doses‖
200-500mg
• Clearer thinking
• Wakefulness
• Better physical coordination
• Reduction of fatigue, and/or
drowsiness
• Enhances endurance-type
exercise performance
―Caffeinism‖ at Higher Doses
~ over 750mg/day
• Habitual use of large amounts of
caffeine, or too much too fast,
results in ―caffeinism‖.
• A condition of chronic caffeine
toxicity or poisoning
associated with
heavy intake of caffeine.
Signs of Caffeinism
• Ringing in Ears
• Insomnia
• Nervousness • Hypertension
• Restlessness • Heart Palpitations
• Irritability • Elevated temperature
• Light flashes • GI disturbances
• Hand Tremors • Convulsions
• Muscle twitching • Heart arrhythmia
• Flushed face • Delirium
*Fatal dose unlikely=10g (~100 cups of coffee)
Tolerance and Dependence
• Tolerance is common with caffeine
• Dependence can occur within a few days
(esp. children) to a couple of weeks.
• Once dependence is established,
withdrawal occurs within 12-24 hours of
the last dose.
• Problems associated with sleep & caffeine
http://www.supermemo.com/articles/sleep.htm#Caffeine
Withdrawal Symptoms
• Headache may last days
• Anxiety & dysphoria
• Rebound Fatigue
Long Term Effects of High Caffeine
Consumption are a Real Problem
• Chronic insomnia • Persistent anxiety
• Irregular heart beat • Depression
• Complications with • Stomach ulcers
pregnancy • Loss of bone mass
• Fibrocystic breast
disease more likely • Increased risk of
heart attack*
* In susceptible patients only
Drawbacks in Sports
At “higher doses” . . .
• Dehydration, due to diuretic action
• Rapid heart rate, over & above exercise
• Jitters; fine muscle movements affected
• Can ―backfire‖ with complex tasks
• Problems with concentration
• Not as helpful for short term activities
as for endurance activities
Reproduction Effects
• May reduce chances
of fertilization
• Slows growth of the
developing fetus in
the first few months
• Developing fetus will
go through (~ week)
withdrawal with a
birth mother who is
dependent