A stimulant drug found in coffee, tea, cocoa, and cola drinks. Caffeine reduces fatigue, improves concentration, makes the heart pump blood faster, and has a diuretic effect. Large quantities may produce side effects such as agitation and tremors. A regular high intake may lead to increased tolerance and withdrawal symptoms, such as headaches and tiredness, after a few hours without caffeine. Caffeine is used in some drug preparations, particularly in combination with analgesics and with ergotamine in preventive treatments for migraine.


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