Caffeine << KAF een >> is an odorless, slightly bitter solid. It is a stimulant, and is found in small amounts in coffee, tea, and colas. Caffeine dissolves in water and alcohol, and has crystals that look like needles. When taken in small amounts, caffeine stimulates the nervous system. In this way, caffeine increases alertness and energy. When taken in large amounts, however, it causes nervousness and loss of sleep. The use of caffeine also may cause headaches and digestive disturbances.
The German chemist Friedlieb Ferdinand Runge first isolated pure caffeine from coffee beans in 1820. It can now be made in the laboratory. As a medicine, caffeine is used as a stimulant of the heart and nervous system in certain disorders. It is also used in some nonprescription pain relievers. Caffeine is also a remedy for poisoning by alcohol, opium, and other drugs that depress (slow down) the nervous system.
