The number of people showing up in emergency rooms for "adverse reactions" to nonalcoholic energy drinks like Amp and Red Bull has shot up tenfold over a four-year period, according to data from the Drug Abuse Warning Network (DAWN) of the federal Substance Abuse and Mental Health Services Administration (SAMHSA). In 2005, DAWN logged just 1,128 emergency department visits involving nonalcoholic energy drinks like Monster, Full Throttle and Rockstar; by 2008 that number shot up to more than 16,000, and in 2009, the most recent year for which DAWN has data, it was 13,114. The problem? Caffeine—a lot of it. The average can or bottle contains up to 500 mg, compared with about 100 mg in a five-ounce cup of coffee or 50 mg in a 12-ounce cola. “There are no safe levels of caffeine,” Dr. Albert Woodward, DAWN's director, tells The Fix. DAWN’s data also found that men are more likely to mix these drinks with alcohol or illegal drugs, while women are more likely to combine prescription drugs with highly caffeinated drinks. And Woodward said younger people have greater access to “central nervous system medications” such as Adderall and other stimulants whose risks are exacerbated when combined with excess caffeine.