Please take time to read "ER visits tied to energy drinks double since 2007." Because of this article, I felt it was a good time to review a previous post about energy drinks and how they can be confused with sports drinks.
Sports drinks vs. energy drinks: Energy drinks are NOT the same as sports drinks. A sports drink is designed to replace water, carbohydrates, and electrolytes during training and competition, and it usually contains no caffeine. An energy drink, on the other hand, has a blend of caffeine and other ingredients including taurine, guarana, and glucuronolactone*^ that are used as stimulants on the central nervous system.
Safety concerns associated with over-consumption of energy drinks: Energy drinks can be dangerous because the amount of caffeine varies greatly by brand, with some having the caffeine content equivalent to 14 cans of soda^. Although it may be easy to attribute all of the negative effects to caffeine, the effect of combining certain stimulants is still unclear and requires more research.
* Higgins JP, Tuttle TD, Higgins CL. Energy beverages: content and safety. Mayo Clin Proc. Nov 2010;85(11):1033-1041.
^ Sports drinks and energy drinks for children and adolescents: are they appropriate? Pediatrics. Jun 2011;127(6):1182-1189.