Roland Griffiths, a psychopharamcologist at Johns Hopkins Medicine in Baltimore told NPR in an interview it is important to recognize caffeine is a mood-altering and behavior-changing drug.
"We're marketing these [drinks] to younger people -- some of whom are relatively new to caffeine or do not consume caffeine at all, and they're essentially instructed, implicitly or explicitly, to 'slam the can,'" Griffiths told NPR.
"As a consequence, we're now seeing acute caffeine overdoses in ways that seem surprising given the prevalence of Starbucks and coffee and soft drinks in our culture. But the difference is that you don't find people walking into Starbucks and gulping down two venti Starbucks. We've been [acculturated] to generally sip these products. And so the onset characteristics are different."
Caffeine intoxication is a diagnostic category usually in excess of 250 milligrams with five or more of the following signs: restlessness, nervousness, excitement, insomnia, flush face, diarrhea, gastrointestinal disturbance, muscle twitching, rambling flow, periods of inexhaustibility and motor agitation, Griffiths said.
"People feel awful; they feel sick, their hearts are pounding or beating irregularly, the feel anxious, it's really unpleasant feeling and can be life-threatening, Griffiths said.
"Most regular caffeine users have developed significant tolerance and so that's why people who are regular coffee consumers think, 'What's the deal here? This is just the equivalent of a venti Starbucks.'"
For those not used to caffeine that's a huge dose, Griffiths said.
"So my thought would be, for someone who's unaccustomed to using caffeine, if they consume an energy drink relatively rapidly, they may get peak blood levels of caffeine in the toxic range," Griffiths said.