"Although the findings of our literature and Internet searches strongly suggest a marked increase in kratom use in the United States and Europe, kratom still appears to be somewhat of an 'underground phenomenon.' During our searches of the literature and the internet, we found no evidence that kratom is currently marketed by any of the large nutritional supplement chain stores in the United States. However, a wide variety of kratom products—including raw leaves, capsules, tablets, and concentrated extracts—are readily available from Internet-based suppliers.20,21 In addition, these products are often sold in specialty stores commonly known as 'head shops' or 'smoke shops.' In February 2012, our own informal in-person and telephone survey of 5 smoke shops in the metropolitan Chicago area revealed that purported kratom products were available in all of them. Figure 2 and Figure 3 show images of several kratom products (ie, chopped leaves, capsules, and pressed tablets) that were legally purchased at a smoke shop in suburban Chicago.
"From a legal standpoint, kratom is regulated as an herbal product under US law and US Food and Drug Administration and US Drug Enforcement Administration (DEA) policies. As of this writing, Mitragyna speciosa (kratom) is not prohibited by the Controlled Substances Act28 and is considered a legal substance in the United States. However, the DEA's December 2010 version of the Drugs and Chemicals of Concern list states that 'there is no legitimate medical use for kratom in the U.S.'29 Therefore, it cannot legally be advertised as a remedy for any medical condition."

Source

Prozialeck, WC, Jivan, JK, and Andurkar, SV. Pharmacology of kratom: an emerging botanical agent with stimulant, analgesic and opioid-like effects. Journal of the American Osteopathic Association. December 2012;112(12):792-9.
https://www.ncbi.nlm.nih.gov/…
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