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Pronunciation | /kæˈfiːn, ˈkæfiːn/ | ||
Other names | Guaranine Methyltheobromine 1,3,7-Trimethylxanthine 7-methyltheophylline[1] Theine | ||
AHFS/Drugs.com | Monograph | ||
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Pregnancy category |
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Dependence liability | Physical: Moderate 13% and variable low–high 10-73%[2] Psychological: Low–moderate[2] | ||
Addiction liability | Relatively low: 9%[3] | ||
Routes of administration | Common: By mouth Medical: intravenous Uncommon: insufflation, enema, rectal, transdermal, topical | ||
Drug class | Stimulant Adenosinergic Eugeroic Nootropic Anxiogenic Analeptic Phosphodiesterase inhibitor Diuretic | ||
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Pharmacokinetic data | |||
Bioavailability | 99%[4] | ||
Protein binding | 10–36%[5] | ||
Metabolism | Primary: CYP1A2[5] Minor: CYP2E1,[5] CYP3A4,[5] CYP2C8,[5] CYP2C9[5] | ||
Metabolites | • Paraxanthine 84% • Theobromine 12% • Theophylline 4% | ||
Onset of action | 45 minutes–1 hour[4][6] | ||
Elimination half-life | Adults: 3–7 hours[5] Infants (full term): 8 hours[5] Infants (premature): 100 hours[5] | ||
Duration of action | 3–4 hours[4] | ||
Excretion | Urine (100%) | ||
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ECHA InfoCard | 100.000.329 | ||
Chemical and physical data | |||
Formula | C8H10N4O2 | ||
Molar mass | 194.194 g·mol−1 | ||
3D model (JSmol) | |||
Density | 1.23 g/cm3 | ||
Melting point | 235 to 238 °C (455 to 460 °F) (anhydrous)[7][8] | ||
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Caffeine (data page) |
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class.[9] It is mainly used as a eugeroic (wakefulness promoter) or as a mild cognitive enhancer to increase alertness and attentional performance.[10][11] Caffeine acts by blocking binding of adenosine to the adenosine A1 receptor, which enhances release of the neurotransmitter acetylcholine.[12] Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors.[13] Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase.[14]
Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related to the adenine and guanine bases of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). It is found in the seeds, fruits, nuts, or leaves of a number of plants native to Africa, East Asia and South America[15] and helps to protect them against herbivores and from competition by preventing the germination of nearby seeds,[16] as well as encouraging consumption by select animals such as honey bees.[17] The best-known source of caffeine is the coffee bean, the seed of the Coffea plant. People may drink beverages containing caffeine to relieve or prevent drowsiness and to improve cognitive performance. To make these drinks, caffeine is extracted by steeping the plant product in water, a process called infusion. Caffeine-containing drinks, such as coffee, tea, and cola, are consumed globally in high volumes. In 2020, almost 10 million tonnes of coffee beans were consumed globally.[18] Caffeine is the world's most widely consumed psychoactive drug.[19][20] Unlike most other psychoactive substances, caffeine remains largely unregulated and legal in nearly all parts of the world. Caffeine is also an outlier as its use is seen as socially acceptable in most cultures and even encouraged in others.
Caffeine has both positive and negative health effects. It can treat and prevent the premature infant breathing disorders bronchopulmonary dysplasia of prematurity and apnea of prematurity. Caffeine citrate is on the WHO Model List of Essential Medicines.[21] It may confer a modest protective effect against some diseases,[22] including Parkinson's disease.[23] Some people experience sleep disruption or anxiety if they consume caffeine,[24] but others show little disturbance. Evidence of a risk during pregnancy is equivocal; some authorities recommend that pregnant women limit caffeine to the equivalent of two cups of coffee per day or less.[25][26] Caffeine can produce a mild form of drug dependence – associated with withdrawal symptoms such as sleepiness, headache, and irritability – when an individual stops using caffeine after repeated daily intake.[27][28][2] Tolerance to the autonomic effects of increased blood pressure and heart rate, and increased urine output, develops with chronic use (i.e., these symptoms become less pronounced or do not occur following consistent use).[29]
Caffeine is classified by the US Food and Drug Administration as generally recognized as safe. Toxic doses, over 10 grams per day for an adult, are much higher than the typical dose of under 500 milligrams per day.[30] The European Food Safety Authority reported that up to 400 mg of caffeine per day (around 5.7 mg/kg of body mass per day) does not raise safety concerns for non-pregnant adults, while intakes up to 200 mg per day for pregnant and lactating women do not raise safety concerns for the fetus or the breast-fed infants.[31] A cup of coffee contains 80–175 mg of caffeine, depending on what "bean" (seed) is used, how it is roasted, and how it is prepared (e.g., drip, percolation, or espresso).[32] Thus it requires roughly 50–100 ordinary cups of coffee to reach the toxic dose. However, pure powdered caffeine, which is available as a dietary supplement, can be lethal in tablespoon-sized amounts.
Results: Of 49 symptom categories identified, the following 10 fulfilled validity criteria: headache, fatigue, decreased energy/ activeness, decreased alertness, drowsiness, decreased contentedness, depressed mood, difficulty concentrating, irritability, and foggy/not clearheaded. In addition, flu-like symptoms, nausea/vomiting, and muscle pain/stiffness were judged likely to represent valid symptom categories. In experimental studies, the incidence of headache was 50% and the incidence of clinically significant distress or functional impairment was 13%. Typically, onset of symptoms occurred 12–24 h after abstinence, with peak intensity at 20–51 h, and for a duration of 2–9 days.
pmid24761279
was invoked but never defined (see the help page).
Boiling Point
178 °C (sublimes)
Melting Point
238 DEG C (ANHYD)
Experimental Melting Point:
234–236 °C Alfa Aesar
237 °C Oxford University Chemical Safety Data
238 °C LKT Labs [C0221]
237 °C Jean-Claude Bradley Open Melting Point Dataset 14937
238 °C Jean-Claude Bradley Open Melting Point Dataset 17008, 17229, 22105, 27892, 27893, 27894, 27895
235.25 °C Jean-Claude Bradley Open Melting Point Dataset 27892, 27893, 27894, 27895
236 °C Jean-Claude Bradley Open Melting Point Dataset 27892, 27893, 27894, 27895
235 °C Jean-Claude Bradley Open Melting Point Dataset 6603
234–236 °C Alfa Aesar A10431, 39214
Experimental Boiling Point:
178 °C (Sublimes) Alfa Aesar
178 °C (Sublimes) Alfa Aesar 39214
abc.net
was invoked but never defined (see the help page).Long-term caffeine use can lead to mild physical dependence. A withdrawal syndrome characterized by drowsiness, irritability, and headache typically lasts no longer than a day. True compulsive use of caffeine has not been documented.
Substance use disorder in DSM-5 combines the DSM-IV categories of substance abuse and substance dependence into a single disorder measured on a continuum from mild to severe. ... Additionally, the diagnosis of dependence caused much confusion. Most people link dependence with "addiction" when in fact dependence can be a normal body response to a substance. ... DSM-5 will not include caffeine use disorder, although research shows that as little as two to three cups of coffee can trigger a withdrawal effect marked by tiredness or sleepiness. There is sufficient evidence to support this as a condition, however it is not yet clear to what extent it is a clinically significant disorder.