What type of drug is it?

Caffeine (C 8 H 10 N 4 O 2 ) is a very common substance that is contained in chocolate, soft drinks, tea, coffee, and can also be purchased as capsules, tablets, or powder. Far and away, though, the way most people use caffeine is through coffee. It is a central nervous system stimulant and is used in most instances to alleviate fatigue or aid concentration.

What is its history?

The first historical record of caffeine use was by the Aztec Indians from the time of Montezuma. Caffeine was used in the form of a hot drink made with cacao (the 'chocolate' tree) leaves and various herbs and spices. Montezuma was said to have drunk up to 50 cups a day. Chocolate, in the form of the chocolate bar, was first introduced by the company Fry & Son in 1847. Coffee, however, proved to be a far more popular form of caffeine intake. It is mentioned in the Koran, the holy book of the Moslem religion and originates from Africa and the Middle East . It was introduced into the United Kingdom originally as a medicine but became extremely fashionable between 1670 and 1730, when there was a massive increase in the number of coffee houses.

How is it used?

As noted above, over the years, coffee, teas and soft drinks have been the most popular methods of taking caffeine. In recent decades, however, over-the-counter "medications" containing caffeine, such as Vivarin and NoDoz have become fairly widespread. Common doses of caffeine range from 50mg. on the low end to 800mg. on the extreme upper end of the spectrum. Comparatively, a cup of coffee contains about 100-150mg. of caffeine.

What are the effects?

Caffeine increases heartbeat, respiration, metabolic rate, and the production of stomach acid and urine; and it relaxes smooth muscles, including the bronchial muscle. These changes vary among people and depend upon the individual's sensitivity to this drug, their metabolism and whether the consumer habitually uses or rarely uses caffeine (ie. their tolerance to the drug). How long the effects last is influenced by the person's hormonal status, whether he/she uses tobacco or takes medications or if they have a disease that impairs liver functioning.
These effects can begin as early as 10-20 minutes after ingestion. Maximum effects are reached in about 30-60 minutes.
There is some evidence linking caffeine heart problems, fibrocystic breast disease(FBD), ulcers and other stomach disorders in regular users. It has also been suggested as a possible cause of cancer and birth defects.

What kind of dependence does it lead to?

Regular caffeine consumption creates a tolerance to caffeine. When the caffeine intake is then reduced, blood pressure drops dramatically, causing an excess of blood in the head (though not necessarily on the brain), leading to a headache.
This headache, well known among coffee drinkers, usually lasts from one to five days, and can be alleviated with over-the-counter analgesics such as aspirin. It can also be alleviated with caffeine intake. Many analgesics, in fact, contain some caffeine.
Other symptoms can include irritability, nervousness, and feeling sleepy, as well as having the caffeine headache.

Physical Dependence:

moderate

Psychical Dependence:

moderate

Tolerance:

moderate