Final results of tests performed by the US Food and Drug Administration (FDA) on 30 kratom products confirm the presence of heavy metals, including lead and nickel, at concentrations not considered safe for human consumption, the FDA said Wednesday.

The FDA first warned of "disturbingly" high levels of heavy metals, including lead and nickel, last November, as reported by Medscape Medical News.

The FDA has posted a list of the kratom products and concentrations of heavy metals found in them on its website.

Based on reported patterns of kratom use, heavy kratom users may be exposed to levels of lead and nickel many times greater than the safe daily exposure, the FDA warns in a statement.

Based on these test results, the typical long-term kratom user could potentially develop heavy metal poisoning, which could include nervous system or kidney damage, anemia, high blood pressure, and increased risk of certain cancers, the agency adds.

"Over the last year, the FDA has issued numerous warnings about the serious risks associated with the use of kratom, including novel risks due to the variability in how kratom products are formulated, sold and used both recreationally and by those who are seeking to self-medicate for pain or to treat opioid withdrawal symptoms," FDA Commissioner Scott Gottlieb, MD, said in the statement.

Gottlieb said the FDA has been "attempting to work" with the companies whose kratom products contain high levels of heavy metals. The agency has released the final laboratory results to the public to "help make sure consumers are fully informed of these risks."

"The data from these results support our public warning about the risk of heavy metals in kratom products. The findings of identifying heavy metals in kratom only strengthen our public health warnings around this substance and concern for the health and safety of Americans using it," he added.

No Approved Use

Kratom is derived from the leaves of the kratom tree (Mitragyna speciosa), which is native to Thailand, Indonesia, and Papua New Guinea. The botanical's popularity has been increasing in the United States, with manufacturers — and those who take it — claiming it can help treat pain, anxiety, depression, and more recently, opioid withdrawal.

Last year, an analysis of kratom by FDA scientists found that its compounds act like prescription-strength opioids. In addition to heavy metal contamination, kratom products have also been found to be contaminated with Salmonella, resulting in numerous illnesses and product recalls.

Kratom has been linked to numerous deaths in the United States. There are currently no FDA-approved uses for kratom, and the agency has advised against using kratom or its psychoactive compounds mitragynine and 7-hydroxymitragynine in any form and from any manufacturer.

Health providers are encouraged to report any adverse reactions related to kratom products to MedWatch, the FDA's safety information and adverse event reporting program.

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