Xanax is a brand name for the medication alprazolam from the benzodiazepine family of drugs. These medications are used to treat anxiety, panic disorders and depression-related anxiety.

Research indicates that pre-race caffeine can improve your performance, especially in endurance contests. As health writer Gina Kolata notes in "The New York Times," researchers have been publishing caffeine studies since 1978. "And in study after study, they concluded that caffeine actually does improve performance."

Occurring naturally in more than 60 plants, caffeine is a bitter substance that when consumed has stimulant properties. According to neurologist Dr. R. E. Shapiro of the University of Vermont, caffeine is the most widely consumed stimulant drug in the world.

If you enjoy occasionally sipping a cup of green tea to make you feel a little more alert during a dull afternoon at work, don't expect that you'll soon need to have a bowel movement. Although caffeine can promote bowel activity, tea doesn't typically have a laxative effect on your digestive system.

Caffeine is readily available in the American diet. According to Harvard School of Public Health, more than 50 percent of American adults consume coffee daily. Popular coffee and tea franchises seem to be on every block, offering a variety of caffeinated beverages.

Several factors, ranging from an underlying medical condition to spasms to medication can cause hand tremors. Caffeine can cause hand tremors if consumed in large quantities or if you have sensitivity to the substance. If you develop hand tremors, see a physician for an accurate diagnosis right away.

Approximately 90 percent of the people in the world consume caffeine in some form, and 80 percent of American adults consume caffeine every day, according to the U.S. Food and Drug Administration.

Caffeine is a natural stimulant found in some plants including the bean of the coffee plant, tea leaves, cocoa beans and the kola nut. It helps postpone drowsiness and stimulates the central nervous system, allowing you to feel more alert and able to concentrate better.

Cymbalta is an prescription drug used in the management of depression, anxiety and other psychiatric disorders. Caffeine, the most widely used stimulant in the world, may alter how your body breaks down Cymbalta. Both caffeine and Cymbalta alter the levels of neurotransmitters in the brain.

Chicory is a root vegetable not unlike the beet. It became popular as a coffee substitute as early as the 18th century when coffee was scarce during the Napoleonic wars. The root of the chicory plant when roasted, dried and ground, can be blended with coffee or substitute for it entirely.

Caffeine is one of the few substances in food that is also considered a drug. Caffeine is found in a variety of drinks such as coffee, tea, soft drinks and energy drinks, as well as in cocoa. It is also present in chocolate, and both prescription and non-prescription medications.

Tylenol is a brand name for acetaminophen, an over-the-counter pain reliever sold in the U.S. and other countries. Tylenol has been used for many years to treat muscle aches, toothaches, arthritis and fever. Caffeine is a nervous system stimulant found in soft drinks, tea, chocolate and coffee.