*Peak X : In 1998, the Food and Drug Administration (FDA) reported having detected a chemical compound known as "peak x" in some 5-HTP products. Peak x had been previously associated with the supplement tryptophan, which is made into 5-HTP in the body.
*Eosinophilia-Myalgia Syndrome : Tryptophan was taken off the market when thousands of people developed a severe blood disorder called Eosinophilia - Myalgia Syndrome (EMS). The cause was later traced to a contaminant found only in batches of tryptophan manufactured by one Japanese company, Showa Denko.
* In addition, taking 5-HTP in combination with certain medications may produce harmful effects. These medications include antidepressant drugs (such as Prozac and Zoloft), dextromethorphan (Robitussin DM, and others), and meperidine (Demerol). 5-HTP may also interact with a number of herbal supplements, including St. John's wort and S-adenosylmethionine.
*Showa Denko, the source of up to 60% of all the tryptophan sold in the United States, had used an untested manufacturing process that reduced the amount of activated charcoal used to filter fermented raw tryptophan. Some reports suggest that purity may be a potential problem for 5-HTP as well. No cases of EMS resulting from 5-HTP use have been reported, however.