chemical compound

Caffeine is a central nervous system (CNS) stimulant. It is in the methylxanthine class. It is found in many plants, and is used in drinks like coffee, some teas, some soft drinks, and energy drinks. It can be harmful for both humans and animals if a large amount is consumed. If a person ate 10-13 grams of caffeine quickly, between 80 and 100 cups of coffee, they would overdose and may die.[11] It is the world's most popular psychoactive drug, and is legal in nearly all of the world.[12]

2D structure of caffeine
3D structure of caffeine
Clinical data
Pronunciation/kæˈfn, ˈkæfn/
7-methyltheophylline[6] Theine
  • AU: A
Physical: low–moderate[1][2][3][4]
Psychological: low[5]
Low[4] / none[1][2][3]
Routes of
By mouth, insufflation, enema, rectal, intravenous
Drug classStimulant
ATC code
Legal status
Legal status
Pharmacokinetic data
Protein binding25–36%[7]
MetabolismPrimary: CYP1A2[7]
Minor: CYP2E1,[7] CYP3A4,[7]
CYP2C8,[7] CYP2C9[7]
MetabolitesParaxanthine (84%)
Theobromine (12%)
Theophylline (4%)
Onset of action~1 hour[8]
Elimination half-lifeAdults: 3–7 hours[7]
Infants (full term): 8 hours[7]
Infants (premature): 100 hours[7]
Duration of action3–4 hours[8]
ExcretionUrine (100%)
  • 1,3,7-Trimethylpurine-2,6-dione
CAS Number
PubChem CID
PDB ligand
ECHA InfoCard100.000.329 Edit this at Wikidata
Chemical and physical data
Molar mass194.19 g·mol−1
3D model (JSmol)
Density1.23 g/cm3
Melting point235 to 238 °C (455 to 460 °F) (anhydrous)[9][10]
  • CN1C=NC2=C1C(=O)N(C(=O)N2C)C
  • InChI=1S/C8H10N4O2/c1-10-4-9-6-5(10)7(13)12(3)8(14)11(6)2/h4H,1-3H3
Coffee plant (Coffea arabica), with fruits. The fruits, which are used to make coffee, contain caffeine.


Caffeine is the main drug that is in coffee. Coffee comes from a tree. The seeds of the tree are roasted to make coffee.

Caffeine comes from other plants as well. It is in guarana, yerba maté, cacao, and some plants used to make tea. The plants use caffeine as a pesticide. This is a chemical that kills insects if they eat the plant. It is the way the plant protects itself.

Caffeine was first extracted from cocoa beans into its purest form which is a white powder and the word originated from the German word “kaffee” and the French word “café” which both mean caffeine.[13]

It is called guaranine when it comes from the guarana plant and theine when it comes from a tea plant. It is called mateine in the mate drink. This drink is an infusion made with Yerba mate.

What caffeine isEdit

Caffeine molecule

Caffeine is a stimulant drug. A stimulant is a drug that increases body actions like heart rate, blood pressure, and metabolism. It makes a person more awake and alert.

Caffeine also is a diuretic. This means it makes a person make more urine (the waste liquid a person makes).

The caffeine chemical is called a xanthine alkaloid. This is a group of chemicals that are stimulants. Some xanthine alkaloids (like theophylline) are used to help asthma.

What caffeine is used forEdit

The biggest use of caffeine is as a stimulant. People drink coffee and other drinks with caffeine to stay awake.

Doctors sometimes use caffeine as a medicine. It is used for headaches (head pain). It is sometimes used to help premature (born very early) babies to breathe. The short-term risk of this treatment seems to be that the babies treated gain less weight than usual.[14]

Caffeine is sometimes given to people after a lumbar puncture. This is a test to see if someone has meningitis.

In the beginning caffeine was found to relieve hunger, so it was used for weight loss. That did not last because people were using too much. Caffeine can be a very dangerous drug when not used in the right way.

Caffeine also has medicinal properties. It is used in many over the counter medicines, such as Excedrin, Midol and Anacin. When combined with other analgesics, caffeine can help to alleviate headaches and cramps.

Problems with caffeineEdit

Caffeine is a problem for spiders. The image above shows a spiderweb which was woven by a normal spider. The image below shows a web of a spider that had received Caffeine in an experiment

The largest problem with caffeine is addiction. This is when people get bad symptoms when they do not have the drug. When people have withdrawal (feel bad because they do not have the drug) they drink more. This makes them feel better. But if they cannot get more, they are likely to feel some of the symptoms listed below:

  • Headaches
  • Being tired or need to sleep
  • Caffeine inhibits sleep and in the long-term alters brain functions
    • Sleep deprivation leads to a weakened connectivity between the amygdala and medial prefrontal cortex which regulate mood and emotion.
      • This causes the consumer to feel irritable, tired, restlessness, and anxious.
  • Nausea (feeling like vomiting)

Caffeine can also hurt people if they drink a lot at once. If someone takes too much of a drug at once it is called an overdose. Caffeine overdose is a medical diagnosis. It is called: Caffeine-Induced Organic Mental Disorder or Caffeine Intoxication. People with this can have these symptoms:

  • Very bad feelings like:
    • Paranoia (feeling as if people are about to hurt the person)
    • Restlessness or nervousness (with the person feeling like he cannot sit down or rest)
    • Anxiety (very bad worry)
  • Muscle movements that cannot be stopped
  • Very fast heart rate
  • Abnormal heart rhythms (even heart stopping)
  • Very high blood pressure
  • Vomiting
  • Confusion (not knowing who the person is or where he/she is)

Caffeine helps forEdit

Caffeine also has some strong advantages:[15]

How much caffeine is safeEdit

250–300 mg of caffeine a day is a moderate amount. That is as much caffeine that is in three cups of coffee (8oz each cup). More than 750–1000 mg a day is a significant amount, but is very unlikely to kill someone. The Lethal Dose 50 of caffeine is 192 mg per kilogram, in rats. In humans, it is between 150 and 200 mg per kilogram (70-90 per pound.)

Caffeine is in many drinks and foods. This is approximate amounts of caffeine in some food and drink:

  • Brewed coffee – 40 to 220 mg in a cup
  • Instant coffee – 30 to 120 mg in a cup
  • Decaffeinated coffee (with most caffeine taken out) – 3 to 5 mg in a cup
  • Tea – 20 to 110 mg in a cup
  • Soda drinks with caffeine – 36 to 90 mg in 12 ounces. Some people think that soft drinks which are light in color do not contain caffeine. This is not always true.
  • Milk chocolate – 3 to 6 mg in an ounce
  • Bittersweet chocolate – 25 mg in an ounce

One ounce – abbreviated oz – is 30 ml.

A 'cup' is 8 oz (240 ml.)

Different ways to get 200mg of caffeineEdit

Caffeine equivalents[16][17]
In general, each of the following contains approximately 200 milligrams of caffeine:


A fluid ounce is between 28 and 30 millilitres.

a. There may also be large amounts of other chemicals, similar to caffeine in Chocolate and other products of cacao. There is theobromine in cacao, for example. These substances can have effects similar to those of caffeine.

b. Most tea drunk in North America is not very strong. The figures are for this kind of tea. The tea drunk in most other places of the world is stronger; for these kinds of tea, the figures are probably too small.


  1. 1.0 1.1 Malenka RC, Nestler EJ, Hyman SE (2009). "Chapter 15: Reinforcement and Addictive Disorders". In Sydor A, Brown RY (eds.). Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York: McGraw-Hill Medical. p. 375. ISBN 978-0-07-148127-4. 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.
  2. 2.0 2.1 Karch SB (2009). Karch's pathology of drug abuse (4th ed.). Boca Raton: CRC Press. pp. 229–230. ISBN 978-0-8493-7881-2.
  3. 3.0 3.1 American Psychiatric Association (2013). "Substance-Related and Addictive Disorders" (PDF). American Psychiatric Publishing. pp. 1–2. Archived from the original (PDF) on 15 August 2015. Retrieved 10 July 2015. 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.
  4. 4.0 4.1 Introduction to Pharmacology (third ed.). Abingdon: CRC Press. 2007. pp. 222–223. ISBN 978-1-4200-4742-4.
  5. Juliano LM, Griffiths RR (October 2004). "A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features". Psychopharmacology. 176 (1): 1–29. doi:10.1007/s00213-004-2000-x. PMID 15448977.
  6. "Caffeine". ChemSpider. Retrieved 16 November 2021.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 "Caffeine". DrugBank. University of Alberta. 16 September 2013. Retrieved 8 August 2014.
  8. 8.0 8.1 8.2 Poleszak E, Szopa A, Wyska E, Kukuła-Koch W, Serefko A, Wośko S, Bogatko K, Wróbel A, Wlaź P (February 2016). "Caffeine augments the antidepressant-like activity of mianserin and agomelatine in forced swim and tail suspension tests in mice". Pharmacological Reports. 68 (1): 56–61. doi:10.1016/j.pharep.2015.06.138. PMID 26721352.
  9. "Caffeine". Pubchem Compound. NCBI. Retrieved 16 October 2014.
    Boiling Point
    178 °C (sublimes)
    Melting Point
    238 DEG C (ANHYD)
  10. "Caffeine". ChemSpider. Royal Society of Chemistry. Retrieved 16 October 2014. 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
  11. "Can caffeine kill you?". 25 September 2012. Retrieved 19 February 2016.
  12. Burchfield G (1997). Meredith H (ed.). "What's your poison: caffeine". Australian Broadcasting Corporation. Archived from the original on 26 July 2009. Retrieved 15 January 2014.
  13. "History and Background". Caffeine. 2012-09-12. Retrieved 2018-11-18.
  14. Schmidt, B; Roberts, RS; Davis, P; Doyle, LW (May 18, 2006). "Caffeine therapy for apnea of prematurity". New England Journal of Medicine. 354 (20): 2112–21. doi:10.1056/NEJMoa054065. PMID 16707748.
  15. "The Advantages and Disadvantages Of Drinking Coffee | Coffee Corner". Coffee Corner. 2017-10-26. Retrieved 2017-12-03.
  16. "Caffeine Content of Food and Drugs". Nutrition Action Health Newsletter. Center for Science in the Public Interest. December 1996. Archived from the original on 2007-06-14. Retrieved 2006-08-22.
  17. "Caffeine Content of Beverages, Foods, & Medications". The Vaults of Erowid. July 7, 2006. Retrieved 2006-08-22.

Other websitesEdit

Scientific informationEdit



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