01Caffeine is a central nervous system stimulant that antagonizes adenosine A1 and A2A receptors, thereby reducing the inhibitory effects of adenosine and promoting wakefulness.
02The half-life of caffeine in plasma is approximately 5 hours in healthy adults, but can extend to 9-11 hours in pregnant women.
03Caffeine increases intracellular calcium levels in skeletal muscle, enhancing contractility and fatigue resistance during exercise.
04At doses of 200-400 mg, caffeine elevates systolic blood pressure by 5-15 mmHg and diastolic by 5-10 mmHg in normotensive individuals.
05Caffeine stimulates the release of catecholamines such as epinephrine and norepinephrine from the adrenal medulla.
06Caffeine inhibits phosphodiesterase, leading to increased cyclic AMP levels and enhanced lipolysis in adipocytes.
07Caffeine crosses the blood-brain barrier within 20 minutes of ingestion, reaching peak plasma concentrations in 30-60 minutes.
08In the liver, caffeine is primarily metabolized by cytochrome P450 1A2 enzyme into three metabolites: paraxanthine (84%), theobromine (12%), and theophylline (4%).
09Caffeine induces diuresis by inhibiting sodium reabsorption in the proximal tubule and increasing glomerular filtration rate.
10Chronic caffeine consumption upregulates adenosine receptors, leading to tolerance to its stimulant effects over time.
11Caffeine enhances alertness by increasing the firing rate of locus coeruleus noradrenergic neurons.
12At high doses (>500 mg), caffeine can cause hypokalemia due to beta-2 adrenergic stimulation shifting potassium into cells.
13Caffeine potentiates the effects of endogenous opioids in the spinal cord, contributing to analgesia.
14Caffeine increases cerebral blood flow velocity by 22-30% at doses of 250 mg.
15Caffeine inhibits GABA_A receptors indirectly, contributing to its anxiogenic effects at high doses.
16Caffeine promotes thermogenesis by uncoupling oxidative phosphorylation in mitochondria via ryanodine receptor activation.
17In neonates, caffeine has a half-life of up to 80 hours due to immature liver metabolism.
18Caffeine enhances dopamine D2 receptor signaling by blocking adenosine A2A receptors that heteromerize with D2.
19Caffeine increases gastric acid secretion by 100% at doses equivalent to 2 cups of coffee.
20Caffeine delays gastric emptying by 20-30 minutes, prolonging exposure of the stomach lining to acid.
21Caffeine stimulates the release of cholecystokinin, enhancing gallbladder contraction.
22At 3-6 mg/kg body weight, caffeine improves reaction time by 5-10% in sleep-deprived subjects.
23Caffeine reduces perceived exertion during exercise by 5-10% via central mechanisms.
24Caffeine increases plasma free fatty acids by 30-50% post-ingestion, sparing muscle glycogen.
25Caffeine antagonizes benzodiazepine binding at GABA_A receptors, reducing sedative effects.
26Caffeine elevates heart rate by 5-10 bpm at doses of 250 mg in habitual users.
27Caffeine inhibits acetylcholinesterase weakly, potentially enhancing cholinergic transmission.
28Caffeine increases alertness and reduces sleepiness by blocking adenosine accumulation during wakefulness.
29Caffeine enhances memory consolidation via increased noradrenergic and dopaminergic activity in the hippocampus.
30Caffeine induces cytochrome P450 1A2 activity after chronic exposure, accelerating its own metabolism.