Caffeine is a commonly consumed drug.
It is found in various beverages such as tea, coffee, cola-flavored carbonated beverages and in chocolate products. Caffeine is also added to a variety of other carbonated beverages and is an ingredient in a number of non-prescription drugs such as headache, cold, allergy, pain relief, and stay awake pills. About 80 percent of the adult population in the US consume caffeine, and about 20 percent consume over 350 mg daily- a level sufficient to cause physical dependency. The method of preparation of tea and coffee determines the caffeine content of the beverage. Physiological effects of caffeine can be seen in adults at doses of only 100-200 mg.