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Summary sheet: Caffeine
Molecular structure of Caffeine.
Chemical Nomenclature
Common names Caffeine, Vivarin, Cafcit, Alert
Substitutive name 1,3,7-trimethylxanthine, methyltheobromine[1]
Systematic name 1,3,7-trimethylpurine-2,6-dione
Class Membership
Psychoactive class Stimulant
Chemical class Xanthine
Routes of Administration

WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.

Threshold 10 - 20 mg
Light 20 - 50 mg
Common 50 - 150 mg
Strong 150 - 500 mg
Heavy 500 mg +
Total 1.5 - 5 hours
Onset 5 - 10 minutes
Peak 1 - 2 hours
After effects 6 - 24 hours

DISCLAIMER: PW's dosage information is gathered from users and resources for educational purposes only. It is not a recommendation and should be verified with other sources for accuracy.

1,3,7-Trimethylpurine-2,6-dione (commonly known as Caffeine) is a naturally occurring, bitter, white crystalline stimulant substance of the xanthine family. It has found widespread use in modern society for its ability to increase activity in the brain and induces temporary improvements including enhanced alertness, wakefulness, and locomotion.

Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants, as well as enhancing the reward memory of pollinators. It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush, as well as from various foods and drinks containing products derived from the kola nut.

Unlike many other psychoactive drugs, this substance is legal and unregulated in nearly all parts of the world. Beverages containing caffeine, such as coffee, tea, soft drinks, and energy drinks, enjoy great popularity. Caffeine is the most commonly used drug in the world, with 90% of adults in North America consuming it on a daily basis. Global consumption of caffeine has been estimated at 120,000 tonnes per year, making it the world's most popular psychoactive substance. This amounts to one serving of a caffeinated beverage for every person every day.[2]


Caffeine, or 1,3,7-trimethylpurine-2,6-dione, is an alkaloid with a substituted xanthine core. Xanthine is a substituted purine comprised of two fused rings: a pyrimidine and an imidazole. Pryimidine is a six-membered ring with nitrogen constituents at R1 and R3; imidazole is a 5 membered ring with nitrogen substituents at R1 and R3. Xanthine contains oxygen groups double-bonded to R2 and R6.

Caffeine contains additional methyl substitutions at R1, R3 and R7 of its structure. These are bound to the open nitrogen groups of the xanthine skeleton. It is an achiral aromatic compound.


Caffeine acts through several mechanisms, but its most important effect is to counteract a substance called adenosine that naturally circulates at high levels throughout the body, and especially in the nervous system. In the brain, adenosine plays a generally protective role, part of which is to reduce neural activity levels.

The principal mechanism of action of caffeine is as a nonselective antagonist of adenosine receptors. The caffeine molecule is structurally similar to adenosine, and is thus capable of binding to adenosine receptors on the surface of cells without activating them, thereby acting as a competitive inhibitor.[3]

Alongside this, caffeine also has profound effects on most of the other major neurotransmitters, including dopamine, acetylcholine, serotonin, and, in high doses, on norepinephrine,[4] and to a small extent epinephrine, glutamate, and cortisol. At high doses, exceeding 500 milligrams, caffeine inhibits GABA neurotransmission. GABA reduction explains why caffeine increases anxiety, insomnia, rapid heart and respiration rate at high dosages.

710px-Caffeine metabolites.svg.png


Caffeine is metabolized in the liver by the cytochrome P450 oxidase enzyme system, in particular, by the CYP1A2 isozyme, into three dimethylxanthines,[5] each of which has its own effects on the body:

  • Paraxanthine (84%): Increases lipolysis, leading to elevated glycerol and free fatty acid levels in the blood plasma.
  • Theobromine (12%): Dilates blood vessels and increases urine volume. Theobromine is also the principal alkaloid in the cocoa bean, and therefore chocolate.
  • Theophylline (4%): Relaxes smooth muscles of the bronchi, and is used to treat asthma. The therapeutic dose of theophylline, however, is many times greater than the levels attained from caffeine metabolism.

Subjective effects

The effects listed below are based upon the subjective effects index and personal experiences of PsychonautWiki contributors. The listed effects should be taken with a grain of salt and will rarely (if ever) occur all at once, but heavier doses will increase the chances and are more likely to induce a full range of effects. Likewise, adverse effects become much more likely on higher doses and may include serious injury or death.

Physical effects

Cognitive effects

After effects
Aftereffects (3).svg

Experience reports

There are currently no anecdotal reports which describe the effects of this compound within our experience index. Additional experience reports can be found here:

Toxicity and harm potential

Caffeine is not known to cause brain damage, and has an extremely low toxicity relative to dose. There are relatively few physical side effects associated with caffeine exposure. Various studies have shown that in reasonable doses in a careful context, it presents no negative cognitive, psychiatric or toxic physical consequences of any sort.

Lethal dosage

Extreme overdose can result in death.[9][10] The median lethal dose (LD50) given orally is 192 milligrams per kilogram in rats. The LD50 of caffeine in humans is dependent on individual sensitivity, but is estimated to be about 150 to 200 milligrams per kilogram of body mass or roughly 80 to 100 cups of coffee for an average adult.[11] Though achieving lethal dose of caffeine would be difficult with regular coffee, it is easier to reach high doses with caffeine pills, and the lethal dose can be lower in individuals whose ability to metabolize caffeine is impaired.

It is strongly recommended that one use harm reduction practices when using this drug.

Tolerance and addiction potential

As with other stimulants, the chronic use of caffeine can be considered moderately addictive with a high potential for abuse and is capable of causing psychological dependence among certain users. When addiction has developed, cravings and withdrawal effects may occur if a person suddenly stops their usage.

Tolerance to many of the effects of caffeine develops with prolonged and repeated use. This results in users having to administer increasingly large doses to achieve the same effects. After that, it takes about 3 - 7 days for the tolerance to be reduced to half and 1 - 2 weeks to be back at baseline (in the absence of further consumption).

Some coffee drinkers develop tolerance to its sleep-disrupting effects, but others apparently do not.[12] Caffeine does not present a cross-tolerance with other common stimulants.

Withdrawal symptoms

Withdrawal symptoms -– including headaches, irritability, inability to concentrate, drowsiness, insomnia, and pain in the stomach, upper body, and joints –- may appear within 12 to 24 hours after discontinuation of caffeine intake, peak at roughly 48 hours, and usually last from 2 to 9 days.[13]Withdrawal headaches are experienced by 52% of people who stopped consuming caffeine for two days after an average of 235 mg caffeine per day prior to that.[14] In prolonged caffeine drinkers, symptoms such as increased depression and anxiety, nausea, vomiting, physical pains and intense desire for caffeine containing beverages are also reported. Peer knowledge, support and interaction may aid withdrawal.


Main article: Stimulant psychosis

There is limited evidence that caffeine, in high doses or when chronically abused, may induce psychosis in normal individuals and worsen pre-existing psychosis in those diagnosed with schizophrenia.[15][16] Caffeine has been shown to potentiate the effects of methamphetamine, which can also induce psychosis.[17][18]

Legal status


This legality section is a stub.

As such, it may contain incomplete or wrong information. You can help by expanding it.

Caffeine is legal in nearly all parts of the world. Because caffeine is a psychoactive substance however, it is often regulated. For example, in the United States the Food and Drug Administration (FDA) restricts beverages to contain less than 0.02% caffeine [19] unless they are listed as a dietary supplement.[20]

See also

External links


  2. What's your poison? Caffeine |
  3. Caffeine as a psychomotor stimulant: mechanism of action |
  5. The Pharmacogenetics and Pharmacogenomics Knowledge Base |
  6. Caffeine ingestion and fluid balance: a review |
  7. Caffeine ingestion and fluid balance: a review |
  8. Caffeine for asthma |
  9. Caffeine fatalities—four case reports |
  10. Alstott RL, Miller AJ, Forney RB (1973). "Report of a human fatality due to caffeine". Journal of Forensic Science 18 (35).
  11. Factors Affecting Caffeine Toxicity: A Review of the Literature |
  12. Actions of caffeine in the brain with special reference to factors that contribute to its widespread use ( / NCBI) |
  13. A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features |
  14. Withdrawal Syndrome after the Double-Blind Cessation of Caffeine Consumption |
  15. Caffeine-induced psychosis |
  16. Psychosis Following Excessive Ingestion of Energy Drinks in a Patient With Schizophrenia |
  17. Caffeine enhances the stimulant effect of methamphetamine |
  18. Interaction between caffeine and methamphetamine by means of ambulatory activity in mice. |
  19. CFR - Code of Federal Regulations Title 21 |
  20. Consumer Q&A: Caffeine-Containing Dietary Supplements |