Contaminant found in ‘safe’ tryptophan derivative 5-HTP

Some commercially available formulations of the dietary supplement 5-HTP, marketed as a "safer alternative" to L-tryptophan, contain the same contaminant that was responsible for more than 1,500 cases of eosinophiliamyalgia syndrome and at least 38 deaths associated with L-tryptophan use in 1989. Patients who take 5-htp (5-hydroxytryptophan) as an antidepressant, sleep aid, or for weight loss or other complaints may be at risk for developing the syndrome. In fact, 10 cases have been reported worldwide, said at a seminar on treating mood and anxiety disorders. Some manufacturers test their products for the presence of the contaminant, which is known as "peak X" because of characteristic findings on gas chromatography. Pa-tients can call the manu-facturer to ask if the product has been tested, said by a director of the psychopharmacology research laboratory, McLean Hospital and Harvard Medical School, Boston. They would only use 5-htp from companies who confirm that their products are peak X-free.

Patients also need to be educated to watch for symptoms of eosinophiliamyalgia syndrome such as muscle pain or weakness, headache, and vomiting, as said at the seminar, which was sponsored by Harvard Medical School. They also need to exercise caution if they are already taking a selective serotonin reuptake inhibitor because inexplicable worsening of mood has been reported in normal control given 5-htp in conjunction with an SSRI. The Food and Drug Administration issued a "talk paper" on 5-HTP in 1998, confirming that peak X had been identified in some products. While the agency has not taken any action to remove the supplement from the market, it has stated that vigilance is warranted. Much of the peak X-contaminated L-tryptophan implicated in the 1980 outbreak ultimately was traced to a single Japanese manufacturer.

L-tryptophan was pulled from the US market in 1990, but remains available by prescription in Canada. The rationale for using L-tryptophan and 5-HTP for depression is that 5-htp is an immediate precursor of the neurotransmitter serotonin. L-tryptophan is metabolized to 5-HTP in the body.

Numerous studies have investigated the safety and efficacy of these products for depression, but most have been flawed. A systematic review suggested that L-tryptophan and 5-HTP may be more effective than placebo, but noted the evidence was of insufficient quality to be conclusive. The starting dose is 300mg twice daily; this can be increased to 300mg three times per day.