5. Caffeine Flashcards
1
Q
What is caffeine?
A
- Naturally occurring compound –> over 60 known plants!
- Most widely used psychoactive drug worldwide
- Member of the methylxanthine family
- adenosine receptor antagonist
2
Q
What are the primary caffeine effects?
A
- Stimulant effect on central nervous system
- Decreased fatigue (keep awake longer)
- Increased mental alertness and concentration
- Improved performance on motor and memory tasks
3
Q
What are the other caffeine effects?
A
- Stimulates acid release from gastric mucosa
- Constricts cerebral blood vessels
- Headache relief: if headache is due to excess pressure in the brain because of extra fluid in the blood vessels. By constricting blood vessels —> squeezes plasma out of central nervous system —> less fluid in the brain —> relief
- Increased heart rate and blood pressure
- Tremors at higher doses
- Mild diuretic effect
- Rapid tolerance develops to this effect
- Not relevant when consumed as a beverage (refer to slide 6)
4
Q
Refer to slide 8-10 for explanation on our body and energy –> caffeine PD
A
other side!
5
Q
What sort of interaction with adenosine receptors would lead to the principle physiological effects associated with caffeine?
A
- activactor/agonist
- we know caffeine is a very strong central nervous simulate. We can recognize it as it is acting on these cells/receptors as an antagonist. By blocking the ability of adenosine to “whisper” cell to slow down —> allows cell to keep going.
- —> caffeine: adenosine receptor antagonist; blocking the ability of adenosine to tell the cell to slow down
- reduced ATP levels (inc adenosine) does not stimulate cell to slow down, so cells continues to deplete energy stores, neurons continue to fire
6
Q
What kind of effects can we expect from a single cup of coffee?
A
- Drug effects are a function of plasma concentration
- The specific conversion factor will vary depending on many factors…
- Individual variability (genetics)
- Temporal variability (time of day, regular user, empty stomach, etc.)
- The specific conversion factor will vary depending on many factors…
- …BUT, as an approximation… refer to slide 13
7
Q
What is the first tangible effect of caffeine? What does increase caffeine consumption lead to?
A
- Adenosine receptor antagonism is the first tangible effect of caffeine
- Most potent concentration-response relationship
- Increased caffeine consumption –> increased adenosine block…
- …BUT, not without side effects as other systems are affected… refer to slide 14
8
Q
What are the side effects of caffeine? (hint: areas of the body)
A
- central (brain)
- irritability
- anxiety
- restlessness
- confusion
- delirium
- headache
- insomnia
- sleep deprivation
- visual
- seeing flases
- ears
- ringing
skin
- inc sensitivity to touch or pain
- muscular
- twitching
- trembling
- overextension
heart
- rapid heartbeat
- irregular rhythm
- respiratory
- rapid breathing
- gastric
- abdominal pain
- nausea
9
Q
Explain the 3 mechanisms of action for the explanation of caffeine side effects.
A
- Phosphodiesterase inhibition –> prevents termination of sympathetic stimulation
- GABAA antagonism –> impedes CNS inhibition, leading to hyperexcitability
- Ca2+ release –> increased cardiac and smooth muscle contractility
*Individuals will differ in susceptibility to side effects!
10
Q
Where does toxic dose lie/begin?
A
- Toxic dose is generally cited as being where these effects are introduced
- Lethal dose ~10 grams of caffeine, equivalent to over 100 cups of coffee!
*please refer to slide 19
11
Q
How is caffeine absorbed and distributed?
A
- Absorption
- Primary route of administration: Oral
- Peak blood concentration (Cmax) within 15 minutes to 2 hours (Tmax)
- Distribution
- Hydrophobic, distributes throughout body
- Crosses blood-brain barrier readily (obviously…)
12
Q
How is caffeine metabolized and excreted?
A
- Half-life of ~3-7 hours
- Longer in neonates, with oral contraception, and in pregnancy
- Shorter with chronic smoking
- CYP450 enzymes in liver
- Predominately CYP1A2 enzyme
- (subtype within larger Cytochrome P450 family)
- ~5% excreted unchanged (via urine)
13
Q
Why do people react differently to coffee or caffeine-containing products?
A
- Pharmacodyamics; adenosine receptor variations have been shown to…
- …affect sensitivity to caffeine
- …correlate with anxiogenic effects of caffeine
- Pharmacokinetics; CYP 450 isozyme 1A2 (CYP 1A2) variations have been shown to…
- …affect caffeine metabolism (“fast” or “slow” metabolizers), influencing likelihood of insomnia
- …alter the interaction between enzyme effects induced by smoking, and caffeine metabolism
- …affect the risk of spontaneous abortion in pregnant women, correlated to metabolism rate
14
Q
Is Caffeine Addictive?
A
- Dependence can certainly occur, but in contrast to “street drugs”…
- …doesn’t threaten physical, social or economic well-being
- …very few users report losing control of caffeine intake
- i.e. “drug seeking behavior” typically associated with street drugs
- Not presently classified as an addictive substance
- Withdrawal certainly can occur
- As little as 1-2 cups per day
- Fatigue
- Irritability
- Headache
- Generally alleviated by caffeine intake
- 2-3 day period in most people
- As little as 1-2 cups per day
15
Q
Is Caffeine Beneficial or Harmful?
A
- Studies suggest both positive and negative effects to caffeine (typically coffee) consumption
- When individual studies are accumulated into meta-analysis (i.e. systematic reviews of the literature), aggregate literature generally suggests positive benefits to coffee consumption or, at worst, no effect
- Cardiovascular Disease
- Stroke
- Heart Failure
- Cancer
- Liver Disease
- Parkinson’s Disease
- Alzheimer’s Disease
- Type 2 Diabetes
