The Food and Drug Administration has issued a warning to consumers about several dietary supplements marketed as “herbal Fen Phen.” The agency stated that these products contain several ingredients which have not been shown to be safe or effective and which may lead to injuries.

The FDA further stated that it is concerned that more consumers will start using herbal Fen Phen following the recent recall of fenfluramine and dexfenfluramine, two medications that were used in the diet drug combination Fen Phen. Both drugs were recalled in September after studies linked them to an increased risk of heart valve damage in patients taking Fen Phen.

According to the new herbal Fen Phen warning, the main ingredient in the over-the-counter supplements is ephedra, which is also known as ma huang. Ephedra is similar to amphetamines and acts as a strong stimulant on the heart and nervous system. The FDA says that it has received more than 800 reports of adverse event reports involving consumers who used supplements containing ephedrine, the active ingredient in ephedra. These reports involved side effects ranging from high blood pressure, irregular heartbeat and tremors to seizures, heart attack, stroke and death.

In addition, some herbal Fen Phen supplements also contain the ingredients St. John’s wort and 5-hydroxytryptophan. The FDA warns that there is little information about the side effects risk of St. John’s wort—which is sometimes known as “herbal Prozac.” The agency also warned of the similarity between 5-hydroxytryptophan and tryptophan, which was taken off of the market in 1990 after it was linked to more than 1,500 cases of a potentially fatal blood disorder known as eosinophilia myalgia syndrome.