- A stimulant found naturally in coffee beans, tea leaves, cocoa beans (chocolate) and kola nuts (cola) and added to soft drinks, foods, and medicines. A cup of coffee has 100-250 milligrams of caffeine. Black tea brewed for 4 minutes has 40-100 milligrams. Green tea has one-third as much caffeine as black tea. Caffeine is an alkaloid. It is metabolized in the liver and the breakdown products of caffeine are excreted through the kidney. In women on oral contraceptives, the rate at which they clear caffeine from the body is considerably slower. Pregnancy reduces a woman's ability to process caffeine still further. The half life of caffeine in an adult is about 3 to 4 hours. In pregnancy, it is 18 hours. In doses of 100-200 mg. caffeine can increase alertness, relieve drowsiness and improve thinking. At doses of 250-700 mg/day, caffeine can cause anxiety, insomnia, nervousness, hypertension, and insomnia. Caffeine is a diuretic and increases urination. It can curiously enough make it more difficult to lose weight because it stimulates insulin secretion, which reduces serum glucose, which increases hunger. Caffeine can help relieve some headaches, so a number of over-the-counter and prescription pain relievers include it as an ingredient, usually with aspirin or another analgesic. The word "caffeine" came from the German Kaffee and the French café meaning, of course, coffee.
* * *An alkaloid obtained from the dried leaves of Thea sinensis, tea, or the dried seeds of Coffea arabica, coffee; used as a central nervous system stimulant, diuretic, circulatory and respiratory stimulant, and as an adjunct in the treatment of headaches. SYN: guaranine, thein.- c. citrate citrated c., a mixture of equal parts of c. and citric acid; more water soluble than c..- c. and sodium salicylate a mixture of sodium salicylate and c. formerly used for the relief of headache and neuralgia.
* * *caf·feine ka-'fēn, 'ka-.; 'kaf-ē-ən n a bitter alkaloid C8H10N4O2 found esp. in coffee, tea, and kola nuts and used medicinally as a stimulant and diureticcaf·fein·ic ka-'fē-nik, .kaf-ē-'in-ik adj
* * *n.an alkaloid drug, obtained from coffee and tea, that has a stimulant action, particularly on the central nervous system. It is used to promote wakefulness and increase mental activity; it also possesses diuretic properties and will help relieve certain forms of headache. It is often administered with aspirin or codeine in analgesic preparations.
* * *caf·feine (kă-fēnґ) (kafґēn) [Ger. Kaffein, from Kaffee coffee] [USP] one of the methylxanthines (q.v.), soluble in water and alcohol, and obtainable from coffee, tea, guarana, and matÐ¹. It stimulates the central nervous system, especially the cerebrum; has a diuretic effect on the kidneys; stimulates striated muscle; and has a group of effects on the cardiovascular system. It is used as a central nervous system stimulant, in combination with ergotamine in the treatment of vascular headache, as an adjunct to enhance pain relief in combination with analgesics, and as an adjunct in the treatment of neonatal apnea; administered orally. Ingestion of excessive amounts can cause caffeinism (q.v.). Called also guaranine and methyltheobromine.
Medical dictionary. 2011.