Caffeine is a stimulant of the methylxanthine class. It is mainly used recreationally to increase alertness in beverage form. Caffeine's structure is similar to that of adenosine, a naturally occurring molecule that has many physiologic effects on the body.[6] Due to caffeine's popularity as the world's most consumed drug, it has been altered to several forms for use such as beverages, pills, and patches.[7]
^Dragoo, K.; Silvers, W.; Johnson, Kelly E.; Gonzalez, E. (2011). "Effects of a Caffeine-Containing Transdermal Energy Patch on Aerobic and Anaerobic Exercise Performance". International Journal of Exercise Science. 4 (2): 7. S2CID34633061.
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^Jamieson, R. W. (2001-12-01). "The Essence of Commodification: Caffeine Dependencies in the Early Modern World". Journal of Social History. 35 (2): 269–294. doi:10.1353/jsh.2001.0125. ISSN0022-4529.