Original article by

Caffeine is a chemical with stimulant properties that is found in many plants including tea, coffee, and guarana. At commonly-used doses it is a mild stimulant and cognitive enhancer that improves focus and mood.

Dose Caffeine is used at dosages ranging from 5-200 mg. On average, a drip-brewed cup of coffee contains 100-150 mg caffeine, a can of cola contains 35-45 mg, and a cup of tea contains 40-60 mg.

Caffeine is widely available both in foods and beverages as well as in inexpensive capsules and tablets.

Caffeine is legal in every country around the world.

Caffeine is a xanthine alkaloid, with a chemical name 1,3,7-trimethylxanthine (C8H10N4O2). Its structure is very similar to the stimulants theobromine (3,7-dimethylxanthine) and theophylline (1,3-dimethylxanthine), which are frequently found in the same plants as caffeine.

When orally administered, caffeine is readily absorbed by the stomach and small intestine. It has a highly-variable elimination half-life, approximately eight to nine hours in adults. It is partially metabolised by the liver into the active dimethylxanthine stimulants theobromine and theophyline, along with other metabolites. Caffeine blockades receptors of the inhibitory neurotransmitter adenosine, and this effect is believed to be the primary mechanism of its stimulant action. Caffeine also disinhibits GABA, the brain's primary inhibitory neurotransmitter.

Throughout caffeine's long history of use, which dates back into pre-history, it has been both praised and damned for its effects. Today caffeine is greeted with near-universal approval and caffeine may well be the most commonly-used psychoactive substance on the planet. Caffeine-producing plants like tea and coffee have been heavily cultivated and have played an important role in commerce throughout recorded history.

Caffeine causes stimulation, arousal, wakefulness, and increased alertness. It increases urine production (diuretic), causes blood vessels to contract (vassoconstrictor), and generally increases blood pressure.

When taken orally, caffeine takes 15-45 minutes to reach its peak effects in the body although stimulant effects are noticeable at 5-10 minutes.

The effects of caffeine are most strongly felt for approximately 2 to 4 hours after onset.

High doses within the normal range of use (250 - 750 mg) can cause insomna, anxiety, tension, nausea, headache, and irregular heartbeat. Very high doses (750 mg - 1 g) can produce toxic symptoms such as nausea, vomiting, tremor, seizures, and irregular heart beat. There are deaths associated with caffeine overdoses, though it is extremely uncommon. The lethal dose for humans has been estimated at between 3-20 grams.

People suffering from ulcers may find that caffeine worsens these problems. Those with generalised anxiety disorder or panic disorder should use caution in consuming caffeine, which may trigger panic attacks in sensitive populations. Pregnant mothers may wish to avoid caffeine. Some studies have found a correlation between moderate caffeine intake and miscarriage while other studies have found no correlation.

Addiction potential
Caffeine use leads to physiological dependency and tolerance. Discontinuation of regular use causes mild to moderate withdrawal symptoms, including sluggishness, fatigue, headaches, mild depression, and sometimes restlessness.

- Article used with the permission of Last modified April 2009.

Erowid caution and disclaimer

This Erowid article is a summary of data gathered from Erowid site visitors, government documents, books, websites, and other resources. As this field is complex and constantly changing, information should always be verified through additional sources.

We live in a world where facts and fiction get blurred
In times of uncertainty you need journalism you can trust. For 14 free days, you can have access to a world of in-depth analyses, investigative journalism, top opinions and a range of features. Journalism strengthens democracy. Invest in the future today. Thereafter you will be billed R75 per month. You can cancel anytime and if you cancel within 14 days you won't be billed. 
Subscribe to News24
Voting Booth
Zama zama crackdown: What are your thoughts on West Village residents taking the law into their own hands?
Please select an option Oops! Something went wrong, please try again later.
Authorities should bring in the army already
11% - 2062 votes
Illegal miners can't be scapegoated for all crime
48% - 8813 votes
What else did we expect without no proper policing
38% - 6979 votes
Vigilante groups are also part of the problem
4% - 679 votes
Rand - Dollar
Rand - Pound
Rand - Euro
Rand - Aus dollar
Rand - Yen
Brent Crude
Top 40
All Share
Resource 10
Industrial 25
Financial 15
All JSE data delayed by at least 15 minutes Iress logo
Editorial feedback and complaints

Contact the public editor with feedback for our journalists, complaints, queries or suggestions about articles on News24.