More than two years after U.S. health regulators discovered an amphetamine-like stimulant in dietary supplements containing Acacia rigidula, products containing the substance remain on the market, a study has found. 

The study, published in the journal Drug Testing and Analysis and made public on Tuesday, found the stimulant beta-methylphenylethylamine, or BMPEA, in more than half of 21 brands of Acacia rigidula supplements purchased a year after the discovery by the U.S. Food and Drug Administration. The study and preparation of the report took another year.

The products tested were marketed for weight loss, athletic performance and to improve brain function, the researchers said. BMPEA has been shown to raise blood pressure and heart rates in dogs and cats but has not been studied in humans. It is classified as a doping agent by the World Anti-Doping Agency because it is closely related to amphetamine.

An FDA spokeswoman, JuliAnn Putnam, said the agency's "first priority" is to ensure dietary supplements are safe and that "our review of the available information on products containing BMPEA does not identify a specific safety concern at this time."

She said the FDA "will consider taking regulatory action, as appropriate, to protect consumers."

Dr. Pieter Cohen, an assistant professor at Harvard Medical School and lead author on the study, said the FDA should warn consumers immediately about BMPEA and take action to eliminate it from dietary supplements.

"Let's not wait until we have a body count," he said. "Just get the job done."

BMPEA is the latest in a series of amphetamine-like stimulants that have appeared in supplements. Cohen said Acacia rigidula, a shrub that is native to Texas, does not naturally contain BMPEA.

The FDA began investigating the product after a study in the late 1990s suggested there could be trace amounts of amphetamine in the plant, Cohen said. The agency found no amphetamine and no BMPEA in the plant itself but high levels of synthetic BMPEA.

"Acacia rigidula is code in the industry for a potent synthetic stimulant," he added. "They are using the name as a cover."

The FDA has tried in the past to keep dangerous stimulants out of supplements. In 2004 it banned the stimulant Ephedra after a decade-long struggle. It subsequently moved to eliminate supplements containing DMAA, a different stimulant also known as 1,3-dimethylamylamine, methylhexanamine or geranium extract.

Now BMPEA is in the spotlight.

Just last week Norcross, Georgia-based Hi-Tech Pharmaceuticals, a leading maker of Acacia rigidula supplements, issued a press release trumpeting its Thermo-RX product, which it claimed "is a quantum leap on the field of weight loss backed by a clinical study".

Companies "have searched high and low" to find an alternative to ephedrine for their weight loss products, the company added. "Acadia Rigidula is not only such an alternative, but it may actually be superior to ephedra."

In November 2013, the FDA seized $2 million in Hi-Tech made products containing DMAA. The company said it has simply switched to using Acacia rigidula.

"Acacia rigidula is just the answer the diet industry has been waiting on for years," the company said.

Hi-Tech said its products are sold through major retailers across the United States.

Last year European regulators ruled that products containing Acacia rigidula could not be legally marketed since they have not been evaluated or authorized. Any company that wants to sell a product containing Acacia rigidula in Europe must demonstrate that it does not present a risk to, or mislead, the consumer.

In December Canadian health regulators ordered the recall of a bodybuilding product called Jetfuel Superburn because it contained amphetamine-like substances, including BMPEA.