A teenage boy was hospitalized with caffeine intoxication after chewing stimulant gum, say Italian doctors who warn the risk to children is high if the readily available products are used excessively.

In the May 30 issue of The Lancet, doctors describe the case of a 13-year-old who was taken to emergency after coming home from school unusually agitated and aggressive.

The boy had abdominal discomfort, increased and painful urination, and prickling sensations in his legs.

When examined, he was restless, with a rapid heartbeat (147 beats per minute), rapid breathing (25 breaths per minute), and elevated blood pressure (145/90 mm Hg). He denied feeling stressed or taking drugs or stimulants.

His chest scans and blood tests normal, and he tested negative for illicit drugs.

He was discharged the next morning with a slow heart beat (40 beats per minute).

Gum wrapper smoking gun

Later that day, his mother came to the hospital with two empty packets of stimulant or energy chewing gum she found in her son's bag. The boy admitted consuming the gum at school within a four-hour period.

The two packs of gum contained a total of 320 milligrams of caffeine — slightly more than three regular cups of coffee.

The boy normally did not consume foods or drinks loaded with caffeine, according to his mother.

"Our patient … presumably had high caffeine sensitivity in view of his low habitual caffeine intake, so 320 mg was a substantial amount of caffeine," wrote Francesco Natale, of the Second University of Naples and Monaldi Hospital in Naples, and colleagues.

For the 45-kilogram boy, the 320 milligrams of caffeine would be equivalent to drinking 10 cups of tea for a 70 kilogram adult over four hours, they noted.

It's unlikely that the other ingredients in the gum played a role, given the low doses and signs and symptoms observed, the doctors said.

Blood caffeine levels were not measured directly but he met the criteria for caffeine intoxication — consuming at least 250 milligrams of caffeine and showing five symptoms.

"The use of stimulant chewing gum should be considered in cases of caffeine intoxication. The risk of intoxication is high in children and teenagers in view of general caffeine-naivety, and the unrestricted sale of these substances," the authors concluded.

Canadian doctors have issued similar warnings about energy drinks.