NEW YORK (Reuters Health) – Warnings should be put on high-caffeine drinks, experts at Johns Hopkins are recommending.

One of the authors of the new research review on these beverages warns that young people who use caffeine-fueled energy drinks may be more prone to illicit use of prescription drugs like Ritalin later on.

Because energy drinks are touted as performance enhancers and stimulants, Dr. Roland R. Griffiths explained in an interview with Reuters Health, kids who use them for these reasons will likely be more open to trying prescription drugs that promise the same effects.

“It seems like it’s a pretty easy threshold to step over, but as a society we want to make this a bright line,” Griffiths said in an interview.

In their report on the marketing, regulation and health effects of caffeinated energy drinks published this month in the journal Drug and Alcohol Dependence, Griffiths and his colleagues at The Johns Hopkins University School of Medicine call for regulations requiring energy drink makers to list the caffeine content of their products on their labels, and warn of the potential for caffeine intoxication.

The first caffeinated energy drink, Red Bull, was introduced in 1987, and now people have hundreds of brands to choose them, the researchers note. The US market for these beverages was $5.4 billion in 2006.

Manufacturers have been able to avoid US Food and Drug Administration (FDA) regulation on labeling by selling their products, which contain from 50 mg to up to 505 mg caffeine per bottle, as nutritional supplements. However, the FDA limits the caffeine content of cola-type beverages to 71 mg per 12 ounces or less, and requires that over-the-counter stimulant medications containing caffeine list their content and include warnings on risks.

Consuming too much caffeine can cause gastrointestinal pain, anxiety and agitation, rapid heartbeat, and insomnia, especially among people who aren’t used to it, the researchers note. The way products are advertised may boost the risk of caffeine toxicity, they add.

“If you look at the advertising, you have expressions like ‘slam the can’ and so forth,” Griffiths said. “People are being encouraged to use these products acutely to boost performance.”

In a press release, the American Beverage Association points out that a 16-oz brewed cup of coffee contains 320 mg of caffeine, compared to 160 mg for a “mainstream energy drink,” and argues that labeling the caffeine content of energy drinks would be a step down a “slippery slope” that would require coffeehouses to provide caffeine content information on their products as well.

According to the ABA, “mainstream responsible players” who make energy drinks containing more moderate amounts of caffeine should not be lumped together with “novelty companies seeking attention and increased sales based solely on extreme names and caffeine content.”

SOURCE: Drug and Alcohol Dependence, September, 2008.