A recent incident report from the federal Food and Drug Administration said energy products like Monster and 5-Hour Energy may have caused up to 18 deaths.

The report has led the FDA to announce last Tuesday an investigation into whether energy products pose a particular threat to teenagers or people with previously existing medical conditions.

“FDA takes every adverse event report seriously and investigates and evaluates other possible causes before deciding whether the product actually caused the medical problem,” the FDA’s report said.

The report lists the incidences of “adverse health” gathered by the Food and Drug Administration that occurred since January 2004 in connection with 5-Hour Energy, Monster, Rockstar and RedBull products. Of the 18 deaths, 13 were associated with 5-Hour Energy products, five with Monster and none with Rockstar or Redbull.

A majority of the incidents involved increased heart rate, headaches, changes in blood pressure, nausea and dizziness, which are all common side-effects of caffeine. Of the 166 incidents reported, 95 were considered serious, life-threatening or required emergency hospitalization.

U.S. Senators Dick Durbin of Illinois and Richard Blumenthal of Connecticut have been trying to convince the FDA since April to put energy products up to further scrutiny.

“There is very clearly a lack of understanding about the health effects of energy drinks and their ingredients especially on children and adolescents,” said Durbin in a letter to the FDA. “I am glad to see that the FDA is undertaking a review but more needs to be done and quickly. For instance, FDA can and should take action now to regulate energy drinks that are marketed as beverages, like Red Bull which has more than the standard of 71 mg of caffeine per 12oz which beverages like Coke and Pepsi are held.”

Energy products can contain anywhere form 50mg to 500mg of caffeine per serving, up to seven times the amount of caffeine in a can of soda.

The products are relatively new to the market, and many are sold as “dietary supplements” rather than conventional foods, which are subject to a much more lenient set of regulations under the Federal Food, Drug and Cosmetic Act.

According to the FDA’s website, dietary ingredients require no FDA pre-approval before being put on the market, and the regulatory legislation puts the burden on the FDA to prove it is harmful before it can be taken off the market.

“The FDA is aware that new products and patterns of use require us to remain vigilant, and we are working to strengthen our understanding of the nature of ‘energy drinks’ and any causal risks to health,” the FDA announced in a letter.

5-Hour Energy, the company whose products were associated with the highest number of adverse incidents, said its products are safe if used responsibly.

“We recommend on product labels and our website that individuals consume no more than two bottles of 5-Hour energy shots per day, spaced several hours apart,” said Elaine Lutz, of Living Essential, a distributor of 5-Hour energy products. “We also recommend individuals new to 5-Hour energy try half a bottle to start, wait 10 minutes and consume the rest later.”