According to the manufacturer, Hi-Tech Pharmaceuticals, Stimerex ES is a highly effective weight loss aid that contains a combination of ingredients, including ephedra, synephrine, green tea extract, theobromine and caffeine. However, as of 2014, there are no available scientific studies proving the company's claims. Further, the ingredients are dangerous according to the National Institutes of Health.
Herbal stimulants used for weight loss have a host of potential side effects, according to the NIH. Ephedra compounds, in particular, are known to cause serious adverse events such as heart attacks, seizures, stroke and even death. These events and other serious side effects are more common when ephedra is taken with other stimulants, such as caffeine. Further, research demonstrates that ephedra supplements are effective only for short-term weight loss, and the Food and Drug Administration has determined that their risks far outweigh their benefits. For this reason, supplements derived from Ephedra sinica, also called ma huang, are illegal in the United States.
Like many supplements marketed in the United States, the ephedra in Stimerex ES isn't derived from Ephedra sinica, but from a source that is legal as of 2014. According to Ephedrine Web, Stimerex ES contains 25 milligrams of ephedra from the Sida cordifolia plant. Stimerex ES also contains synephrine, a chemical derived from the bitter orange plant. WebMd warns that synephrine hasn't been proven to be any safer than ephedra and may cause high blood pressure and elevated heart rate in healthy adults when taken with caffeine.