Dietary supplements containing kratom have been seized in the United States

 ”Mitragyna speciosa”, commonly known as kratom, is a botanical substance that grows naturally in Thailand, Malaysia, Indonesia and Papua New Guinea. Besides mitragynine, there are more than 40 compounds in M. speciosa leaves, including many alkaloids such as mitraphylline, 7-hydroxymitragynine, and

mitragynine pseudoindoxyl. Other active chemicals in M. speciosa include raubasine (best known from Rauwolfia serpentina) and some yohimbe alkaloids such as corynantheidine. M. speciosa also contains at least one alkaloid (rhynchophylline) that is a calcium channel blocker, and reduces NMDA-induced current. The amount of mitragynine within the leaves depends highly on many factors, one major factor is the location of the tree. When trees are grown in Southeast Asia, the levels tend to be higher but when grown elsewhere (even in greenhouses) the levels tend to be low or non-existent. One analysis of products marketed as kratom leaf found, using liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS), mitragynine at levels of 1–6% and 7-hydroxymirtrogynine at levels of 0.01–0.04%. The chemical structure of mitragynines incorporate the nucleus of the tryptamine, and these may be responsible for the molecules observed in the serotonin and adrenergic systems. The pharmacological effects of kratom on humans are not well studied. Its metabolic half-life, protein binding, and elimination characteristics are all unknown. Kratom behaves as a μ-opioid receptor agonist, similar to opiates like morphine, although its effects differ significantly from those of opiates.

Serious concerns exist regarding the toxicity of kratom in multiple organ systems. Consumption of kratom can lead to a number of health impacts, including, among others, respiratory depression, vomiting, nervousness, weight loss and constipation. Kratom has been indicated to have both narcotic and stimulant-like effects and withdrawal symptoms may include hostility, aggression, excessive tearing, aching of muscles and bones and jerky limb movements.In February 2014, the FDA issued an import alert  that allows U.S. officials to detain imported dietary supplements and bulk dietary ingredients that are, or contain, kratom without physical examination.In January 2016, the FDA administratively detained RelaKzpro under the Federal Food, Drug and Cosmetic Act (FD&C Act), as amended by the Food Safety Modernization Act (FSMA). Under its administrative detention authority, the FDA can detain a food or dietary supplement product if the agency has reason to believe the product is adulterated or misbranded. The agency can keep detained products out of the marketplace for a maximum of 30 days while it determines whether to take further enforcement action, such as seizure. The U.S. Department of Justice, on behalf of the FDA, filed a complaint in the U.S. District Court for the Northern District of Illinois alleging, among other things, that kratom is a new dietary ingredient for which there is inadequate information to provide reasonable assurance that it does not present a significant or unreasonable risk of illness or injury; therefore, dietary supplements containing kratom are adulterated under the FD&C Act.