A new stimulant drug that has never been tested in people can be found in 12 weight loss and sports supplements, some of which are sold in mainstream vitamin shops, according to a new study.

The synthetic compound, called 1,3-dimethylbutylamine (or DMBA), often listed on labels as AMP Citrate, is extremely similar to another stimulant called DMAA, the researchers say. In 2012, the Food and Drug Administration banned DMAA because of reports of its side effects, including heart problems, nervous system disorders and even death.

In the new study, the researchers found that 12 out of the 14 weight loss and sports supplement products that they tested contained large amounts of DMBA, in the range of 13 to 120 milligrams per serving. Molecules of DMBA are very structurally similar to those of DMAA, but with some tweaks, such as one fewer carbon atom, the researchers said. The compound has only been tested in a few animal studies, the researchers said. [Dr. Oz's 'Miracle' Diet Pills: 5 Controversial Supplements]

It is concerning that many consumers may be using these supplements, unaware that they contain untested stimulants, said Dr. Pieter Cohen, an assistant professor of medicine at Harvard Medical School and a general internist at Cambridge Health Alliance in Boston, who co-authored the new study.

"There's not a single experiment that we are aware of, in which this substance was given to humans," Cohen told Live Science.

Because of the structural similarity of DMBA to DMAA, it is highly possible that the drugs have similar effects, Cohen said. Both drugs can be stimulating in a way similar to amphetamines, but have different chemical structures from that class of compounds.

The products that the researchers found to contain DMBA were marketed for their supposed ability to improve people's athletic performance, aid weight loss and enhance brain function, the researchers said in their study, published today (Oct. 8) in the journal Drug Testing and Analysis.

Supplements containing DMBA

One of the products in the study is a powder called Frenzy, which is described by retailers as the sequel to a product called Craze. Last year, studies found that Craze contained undisclosed methamphetamine-like compounds. Driven Sports, the manufacturer of Frenzy and Craze, received a warning letter regarding Craze from the FDA in April.

Now, Craze is off the shelves, but Frenzy is still sold in Europe. The supplement gives consumers "endless energy," "extreme focus" and "tunnel vision," according to online comments from consumers, many of whom described the effects of Frenzy as very similar to those of Craze.

A representative for Driven Sports spoke with Live Science and defended Frenzy by saying that the new study was not peer-reviewed, meaning that it wasn't reviewed by scientists other than the authors.

But the journal does, in fact, use a peer-review system. "It's a chemistry journal, and the article went through rigorous peer review," Cohen said.

The other supplements in the study found to contain DMBA include: Contraband (made by Iron Forged Nutrition), Redline White Heat and MD2 Meltdown (made by Vital Pharmaceuticals Inc., which distributes the supplements under the brand name VPX), Evol and Decimate Amplified (made by Genomyx LLC), Oxyfit Xtreme and Synetherm (sold at planetarynutrition.com), AMPitropin and AMPilean (made by Lecheek Nutrition), OxyTHERMPro (made by deNOVOLABS) and OxyphenXR AMP'D (made by Beta Labs Ltd.). Live Science reached out to these companies for comment where contact information was available, but did not hear back by press time.

DMBA came to the researchers' attention when a consumer in the Netherlands notified health authorities about the side effects, such as feeling jittery, after using a supplement called Unstoppable, the researchers said.

There are several other names that are used for DMBA, such as AMP Citrate and 4-amino-2-methylpentane citrate. For the study, the researchers looked for dietary supplements that listed one of these names as an ingredient on their label. (An entirely different drug that is used in cancer studies is also called DMBA, but has a different full name and chemical structure.)

The research team purchased two containers of each product. One was analyzed by the NSF International laboratory in Ann Arbor, Michigan, and the other was analyzed by the Netherlands' National Institute for Public Health and the Environment.

It turned out that two out of the 14 products, Preamp by Hybrid (from DSEO LLC) and AMP Citrate (from Genomyx LLC), did not contain DMBA, according to the study.

The researchers said they focused their study on products sold by U.S. distributors (with the exception of Frenzy), which is likely a fraction of the whole picture, they said. [The Drug Talk: 7 New Tips for Today's Parents]

"There are likely many more sold by European and Australian distributors, and there are likely many that don't list the AMP or AMP Citrate on the label," Cohen said.

Where does DMBA come from?

Two of the products examined, Frenzy and OxyphenXR AMP'D, described DMBA on their label as if it were a compound extracted from a type of tea called Pouchong tea, the researchers said.

"This is beyond belief; it stretches the imagination," Cohen said. Even if the tea happens to contain small amounts of DMBA, this would not explain how such large doses ended up in the supplements, he said.

"It would be physically impossible to get enough tea to make even the lowest dose," Cohen added. "You would require a thousand kilograms [2,200 lbs.] of the tea."

The amounts found in the supplements suggest that DMBA is synthetically mass-produced to create pharmaceutical effects, the researchers said.

A website that appears to be based in China claims to sell large doses of DMBA. It describes DMBA as a substitute product developed to replace the now-banned DMAA.

How to stay safe?

The researchers called on the regulatory agencies to warn consumers and remove DMBA from all dietary supplements.

But in the meantime, consumers who take supplements can't do much to avoid untested drugs, because new drugs replace those that have drawn attention, Cohen said.

"It's impossible for consumers to be able to tell by reading the label which has experimental drugs in it, and which doesn't," Cohen said. "What consumers can do would be to avoid using any supplement that's being sold as if it's going to improve your athletic performance, help you lose weight or sharpen your thinking."

Email Bahar Gholipour. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.