Chapter 9: Caffeine and the Methylxanthines Flashcards
What are the three naturally occurring Methylxanthines?
- Caffeine
- Theophylline (tea)
- Theobromine (chocolate)
What is the source of coffee?
two most common species?
From the fruit of a bush or small tree of the genus Coffea……
- Coffea arabica
- Coffea canephora
Things that factor in the production of coffee?
- beans are roasted (enhances flavour)
- caffeine concentration in the coffee beans, method of brewing, size of cup
Average cup of coffee contains how much caffeine?
100-200mg
avg = 133mg
What is the source of tea?
- leaves from Camellia Sinesis
- only the bud and first two leaves of each twig are used for good quality tea..
- inferior cups are made from the third and fourth leaves.
Black or fermented tea ???
-leaves are dried, crushed and left to oxidize…crushing breaks the membrane and releases enzymes that cause oxidation turning the leaves slightly black
Semifermented or oolong tea?
- oxidation is not allowed to go to completion via roasting it
Unfermented tea?
green tea/ Chinese tea
- leaves are steamed soon after picking and before drying to prevent oxidation
Amount of caffeine in tea?
9-91mg ….average 27mg
Coca comes from?
Theobroma cocao tree.. found in the Amazon rain forest..
-mostly cultivated in Central and South America, the west indies and west Africa
Production of cocoa?
Seeds are removed
- undergo fermentation causing them to germinate and die, then they are dried out.
- roasted to enhance flavour
- crushed = solid unsweetened chocolate
How do they get rid of the high fat content in the chocolate?
- press developed by Houten
- also alkalized cocoa which gave it a richer flavour and darker colour
Other natural sources ?? and cultivated areas?
- Guarana
- Kola nuts
-paste made from the seeds of Paullinia cupana which contains 2-6% caffeine
L> cultivated in Amazon, Orinco and Negro rivers SA.
-Cola trees = Kola Nuts…edible and contain caffeine
Both Theophylline and caffeine are used as _____ for new born babies and people suffering from ____.
- respiratory stimulants
- asthma
Kola nut in 1885 was originally used in what?
Coca Cola
How much caffeine was in Coca Cola in 1885..
- 35-50mg
What does the FDA have set as the allowed amount in soft drinks caffeine wise?
71mg in a 12-oz serving..
How did energy drinks get around the FDA’s limit on caffeine?
- advertised as dietary supplements etc which are not covered by the FDA
Energy drinks contain on avg how much caffeine?
- 50 to 300mg
Additives in Energy drinks are?(5)
- ginkgo, guarana, kola nut, maté and cocoa.
extra caffeine not included on the label
Who was the first person to drink coffee in England and what did his colleagues suggest about coffee?
- William Harvey
- cure for drunkenness
Coffee drinking in the UK caused a decline in?
- consumption of alcoholic beverages, particularly cheap gin.
Who is credited with the discovery of tea??
Chinese emperor Chen Nung
- sold commercially by 780 CE
Who brought tea to England?
Infanta Catherine…marrying Charles II
What caused smuggling in Britain?
- tax imposed on tea via the English Parliament at Westminster
What fumed the fires in the hearts colonists in America to perform “tea parties”
- tea surplus and direct tax …. Boston Harbour
Who first cultivated the coca tree? (3)
Aztecs, Mayans and the Incas
Cocoa was largely believed to be a ___.
aphrodisiac
Which of the following was introduced to Europe first:
Coffe
Tea
Chocolate
chocolate!!!!! ^_^ om nom nom
Who are the two greatest parts of the world in terms of methylxanthine use?
Ireland and Great Britain
The average consumption of caffeine in the world is ?
70mg per person per day …….. 90% from tea and coffee
In the USA whats the order for caffeine consumption ??
Coffe>soft drinks> tea> and others including cocoa
The purified drugs sometimes can cause? (2)
who is at the greatest risk of these side effects?
- nausea, gastric irritation
- children
In purified state the drugs can be administered how?? (3)
- rectal suppository, intramuscular or intravenous routes
Methylxanthine’s are ____ absorbed from ____ and____, totally ____/
completely, stomach, intestine, unionized
Absorption occurs more rapid through the wall of the?
intestines
What slows emptying time in the stomach and consequently absorption?
- presence of food
The methylxathines have a very low pKa of ____. This means what?
- 5
- will not ionize at all and will be free to dissolve in any tissue in accordance with their lipid solubility.
Caffeine is consumed in its ___ form?
-alkaloid
For medicinal reasons it is given as ___?
salts which can be absorbed much more readily
Aminophylline?(4)
treats?
mixture of? (2)
(latter of mixture functions as?)
- bronchodilator treats asthma..
- mixture of theophylline and ethylenediamine
- ethylenediamine increases the amount of dissolved theophylline 20 times..speeding absorption
After drinking coffee or tea, caffeine is completely absorbed in the intestine and peak blood levels are reached in?
~ 30 mins
Caffeine crosses the ? With great ease..
blood brain barrier and placental barrier
What causes caffeine to be trapped in the blood? how much does?
- protein binding …..
10-30%
Are Theophylline and theobromine less, equally or greater in lipid solubility compared to caffeine
- less lipid soluble…slower getting through the blood brain barrier..
How much caffeine is excreted unchanged in urine of humans?
X>2%
The half life of caffeine mean is??
3.5 hours
The half lives of theophylline and theobromine are considerably longer…..what is it?
- 6.2 and 7.2 hours
What is the genetic significance of having either of the two CYP1A2 genes?
CYP1A21A
CYP1A21F
- rapid caffeine metabolizers
- slow caffeine metabolizers
_ therefore the same amount of caffeine will have a greater affect on those with 1F than the 1A and will probably have more side effects
In women metabolism is closely related to hormone levels..
- Half life is longer during what phase of the menstrual cycle?
- Half life is 2x when oral ______ are taken in women vs during the menstrual cycle.
- What also slows absorption in women?
- luteal phase - after ovulation not during the follicular phase which is before ovulation
- contraceptives
- pregnancy
Metabolism of caffeine in new borns is _____ via?
this does not change until what age?
poor
the fact that they leave 85% of the caffeine unchanged in urine
7-9 months
Methylxanthines are _____ blockers… therefore effecting what?
adenosine receptor
- reuptake, in direct modulation
What is adenosine? A1 A2a A2b A3
- inhibits neurotransmission in many synapses…. at postsynaptic synapses acts as a NT
A1 and A2a adenosine receptors appear to regulate what?
dopamine levels
- methylxanthines increase dopamine availability
Receptor mosaics? wtf
- modulate the release of dopamine, glutamate and acetylcholine
- when two or more receptors become attached to each other, influencing each others operations
Methylxanthines are also known to block what receptors?
BZD receptors
Chocolate contains other substances that resembles ____ ?
- anandamide which is the endogenous transmitter that works at cannabinoid receptors
Methylxanthines cause the release of what ? which stimulates what?
- epinephrine
- stimulates the sympathetic nervous system
Much of caffeines effect outside the CNS is due to what?
- direct effect on the muscles smooth (invol) muscles tend to relax and striated (vol) muscles are strengthened
Caffeine can ____ mood and makes tasks seem ___ which leads the subject to believe their performance has _____ when in actuality it hasn’t.
- increase, easier, increased
performance may be influenced via?
placebo effects
Caffeine is capable of reversing performance decrements caused by what??(4)
- boredom and fatigue
- drugs
- caffeine withdrawal
- the common cold
Caffeines effect on athletic performance? (2)
improvements? no improvement?
- no improvement in events that require muscle strength or intense output or short duration.
- Improvement in tasks that require sub-maximal output for an extended period of time.
What are the four effects Methylxanthines have on sleep??
- methylxanthines increase the length of time it takes to fall asleep and decreases total sleep time.
- Caffeine decreases subjective quality of sleep
- caffeine users before sleep wake up more easily in response to sounds.
- Caffeine can counteract the sleep inducing effects of pentobarbital
Subjective effects of caffeine findings are?
confusing and contradictory research findings
Positive effects of caffeine are detected under very restrictive conditions: (3) - Subjective effects
for one think dosage level!
- seen when administered to nonusers or users that have been deprived over night
- low doses (20-200mg) yield positive effects whereas unpleasant effects are seen the higher the dose!
- effects have also been seen in street use when they are given coffee IV
Chronic caffeine causes an _____ regulation of adenosine receptors
up
Human users show differences in the responses of heavy coffee drinkers vs nonusers….huh?
-caffeine has less an effect on heavy drinkers than nonusers
Different effects of caffeine show tolerance at different rates…. 3
- Cardiovascular effects disappear within 2-5 days
- tolerance to caffeine induced urination may take much longer
- many effects of caffeine disappear within a weak of usual lvls of consumption
Tolerance to the sleep disrupting effects of caffeine dosages of 400mg dissipates at
- 7 days
Tolerance to the subjective effects of 300mg develop at ?
4 days
The most common symptoms of withdrawal from caffeine are?
- headache
- drowsiness, decreased energy and fatigue
The not so common withdrawal symptoms of caffeine? - 6 main ones
- decreased motivation for work and impaired concentration, decreased feelings of well being and self confidence, increased irritability, and flu like symptoms ( aches, muscle stiffness, hot and cold spells, heavy feelings in limbs and nausea)
The severity of withdrawal symptoms is directly related to what?
-the persons usual dosage
Doses as high as ____mg can cause physical dependance after ____-____ days of exposure.
600, 6-14
Doses as low as ____mg taken over a longer period can cause ______.
100mg, withdrawal symptoms
Withdrawal symptoms start after ___-___ hours from the last dose and peak at __-__ hours and last 2-9 days.
- 12 to 28 hours, 20 to 51 hours
Self administration in humans?
- Whether or not caffeine is ____?
- low doses are?
high doses are ?
- is reinforcing varies considerably person to person
- usually reinforcing (100mg)
- usually avoided ( 400-600)
Caffeine intoxication?
1. Doses of ____ and higher can cause ___ and ___ but usually only in those with problems already pertaining to PD and AD. This is not see in ___ individuals unless used ___.
300mg, panic, anxiety, normal, excessively
Caffeine intoxication continued
2. Doses of __g and higher per day can result in what symptoms? 6
- 1 gram, agitation, twitching, rambling, flow of thoughts and speech and irregular heart rhythms
At does of 5 to 10 cups a day caffeine can cause symptoms such as: ? (caffeinism/ caffeine intoxication)
-ringing in the ear,seeing flashes of light, as well as mild delirium and excitement
Beneficial Effects:?
Parkinson’s Disease? 2
Why does this occur??
caffeine may have positive effects against parkinson’s disease lower incidence and symptoms such as tremors and the deterioration of motor skills.
- caffeine increases dopamine activity via blocking adenosine receptors (parkinsons is caused by a deficiency in DA)
Beneficial effects part 2?
- prevention of what?
caffeine consumption has been related to reduce risk of developing type 2 diabetes
-decaffeinated as well but not as strong results
Beneficial effects part 3
weight?
- caffeine consumption may promote weight loss or prevent weight gain due to increase metabolic activity and increased energy expenditure
Lethal effects of caffeine???
how high of dose required? - g
death results via?
3-8g
convulsions and respiratory collapse
