Lecture 6.2 Caffeine

Caffeine type of drug (1)

stimulant

caffeine route of administration (1)

oral

caffeine duration of effect (1, 12)

moderate (~4h half-life; individual genetic variability)

caffeine neurotransmitter directly affected (1)

adenosine

caffeine tolerance (1)

some

caffeine physical dependence (1)

some

caffeine psychological dependence (1)

some

caffeine withdrawal symptoms (1)

anxiety, lethargy, headache, fatigue

caffeine scehdule (1)

legal

caffeine family (4)

xanthine; group of alkaloids used for their milk stimulant effects

what plants have caffeine? (4)

over 60 species of plants; e.g., coffee bean, tea leaf, kola nut, cocoa bean

most common source of caffeine for adults (9)

coffee

most common source of caffeine in children and adolescents (9)

soft drinks; use has declined since 2004

how fast is caffeine absorbed from the GI tract? (10)

30-60 minutes

two major caffeine metabolites that have similar stimulant properties (11)

theophylline and paraxanthine

problems with SSRIs and caffeine (11)

some inihibit caffeine metabolism by inhibiting the enzymes

caffeine enzymes (11)

CYP-1A2 subgroup

how fast is caffeine eliminated? (12)

2-10 hours in adult humans

caffeine and oral contraceptives (12)

doubles the half life of caffeine (stays around longer)

caffeine half life in smokers (12)

shortened; may contribute of cigarette withdrawal symptoms

effects of caffeine (why do most people consume caffeine?) (13)

enhanced attention; increased concentraion; reduced fatigue; alleviation of withdrawal symptoms; facilitates athletic performance

physiological effects of caffeine (14)

depends on tolerance; stimulates the CNS; causes sleep disturbances; elevates mood; constricts blood vessels in the brain; relaxes GI muscles

symptoms of excessive use of caffeine (15)

nervousness/anxiety; irritability; tremors/muscle twitching; seiaures; insomnia; flushed appearance; elevated temperature, breathing; palpitations/heart arrhythmias; fastrointestinal disturbances; dehydration

toxic/legal dose of caffeine (15)

3 to 5 grams or more

timeline of caffeine withdrawal symptoms (17)

appear rapidly but dissipate after a few days

role of adenosine (18)

important in the production of sleep; decreases neuronal activity and dilates blood vessels, creating sedation

caffeine mechanism of action (18)

adenosine antagonist (blocking A₁ and A_2A receptors) causing increased brain activity and a feeling of alertness

role of A_2A receptor (19)

occupancy by adenosine exerts an allosteric influence on the D₂ receptor, reducing its affinity for DA and decreasing the effects of DA

caffeine and A_2A receptor (19)

blockade of the A_2A receptor by caffeine causes behavioural stimulation

caffeine and GABA receptors (20)

at higher doses and concentrations, caffeine can block GABA receptors and block Ca2+ release

additional uses for caffeine (21)

pain relief (e.g., treatment for migranes); treatment for hyperactivity (ADHD), use in soldiers; treament of newborns with sleep apnea. used erroneously to sober up

health benefits of caffeine (22)

sharper brain function; may improve fat metabolism; enhances exercise performance; potential decreased risk of diabetes and heart disease; improved mood

high caffeine consumption reproductive health risks (24)

reduces the chance of becoming pregnant; may slow the growth of the fetus; may increase the risk of miscarriage or stillbirth

caffeine intoxication (25)

cause by excessive caffeine consumption; characterized by symptoms such as twitching, disordered thought and speed, and cardiac arrhythmia