Mitragyna speciosa is a tropical evergreen tree of the Rubiaceae family (coffee family) native to Southeast Asia. It is indigenous to Cambodia, Thailand, Indonesia, Malaysia, Myanmar, and Papua New Guinea, where its dark green, glossy leaves, known as kratom, have been used in herbal medicine since at least the 19th century. They have also historically been consumed via chewing, smoking, and as a tea.
The efficacy and safety of kratom are unclear. In 2019, the US Food and Drug Administration (FDA) stated that there is no evidence that kratom is safe or effective for treating any condition. Some people take it for managing chronic pain, for treating opioid withdrawal symptoms, or for recreational purposes. The onset of effects typically begins within five to ten minutes and lasts for two to five hours. Kratom contains over fifty —primarily mitragynine and 7-hydroxymitragynine—which act as at μ-opioid receptors with complex, receptor-specific effects and additional interactions across various neural pathways.
Anecdotal reports describe increased alertness, physical energy, talkativeness, sociability, sedation, changes in mood, and pain relief following kratom use at various doses. Common include appetite loss, erectile dysfunction, nausea and constipation. More severe side-effects may include respiratory depression (decreased breathing), seizure, psychosis,
As of 2018, kratom is a controlled substance in sixteen countries. Some countries, like Indonesia and Thailand, have recently moved toward regulated legal production for medical use. There is growing international concern about a possible threat to public health from kratom use. In some jurisdictions its sale and importation have been restricted, and several public health authorities have raised alerts. Kratom is under preliminary research for possible antipsychotic and antidepressant properties.
Mitragyna speciosa is indigenous to Thailand, Indonesia, Malaysia, Myanmar, and Papua New Guinea. It was first formally described by the Dutch Empire botanist Pieter Korthals in 1839, who named it Stephegyne speciosa; it was renamed and reclassified several times before George Darby Haviland provided the final name and classification in 1859.
Kratom is commonly ingested by chewing, as a tea, powdered in capsules or pills, or for use in liquids. Kratom is rarely smoked. Different varieties of kratom contain different relative proportions of such as mitragynine.
Kratom is often used by workers in laborious or monotonous occupations to stave off exhaustion and as a mood-enhancer and painkiller. In Thailand, kratom was "used as a snack to receive guests and was part of the ritual worship of ancestors and gods". The herb is bitter and is generally combined with a sweetener.
Data on how widely it is used worldwide are lacking, as it is not detected by typical drug screening tests. Rates of kratom use appear to be increasing among those who have been self-managing chronic pain with opioids purchased without a prescription and are cycling (but not quitting) their opioid use.
In 1836, kratom was reported to have been used as an opium substitute in Malaysia. Kratom was also used as an opium substitute in Thailand in the 19th century.
According to the U.S. DEA and a 2020 survey, kratom is used to alleviate pain, anxiety, depression, or opioid withdrawal.
In Thailand, a 2007 survey found that the lifetime, past year, and past 30 days kratom consumption rates were 2.32%, 0.81% and 0.57%, respectively, among respondents aged 12–65 years, and that kratom was the most widely used recreational drug in Thailand.
Kratom may be mixed with other psychoactive drugs, such as caffeine and codeine. Starting in the 2010s, a tea-based cocktail known as "4×100" became popular among some young people across Southeast Asia and especially in Thailand. It is a mix of kratom leaves, cough syrup, Coca-Cola, and ice. Around 2011, people who consumed the cocktail were often viewed more negatively than users of traditional kratom, but not as negatively as users of heroin. As of 2012, use of the cocktail was a severe problem among youth in three provinces along the border of Malaysia and southern Thailand.
In the U.S., , kratom was available in outlets such as and over the Internet; the prevalence of its U.S. use was unknown at the time. In the United States, kratom use increased rapidly between 2011 and 2017. By 2020, it was estimated that 15 million people worldwide use kratom.
Kratom products in the U.S. are commonly used in doses of 2–6 g of dried leaf, and doses exceeding 8 g are relatively uncommon. Given that kratom products may vary greatly in potency, there is no standard dosing system. At relatively low doses (1–5 g of raw leaves), at which there are mostly stimulant effects, side effects include contracted pupils and blushing; adverse effects related to stimulation include anxiety and agitation, and opioid-related effects such as itching, nausea, loss of appetite, and increased urination begin to appear. At moderate to high doses (5–15 g of raw leaves), at which opioid effects generally appear, additional adverse effects include tachycardia (an increased stimulant effect) as well as the opioid side effects of constipation, dizziness, hypotension, dry mouth, and sweating.
Long-term use of high doses of kratom may lead to development of tolerance, dependence, and withdrawal symptoms, including loss of appetite, weight loss, decreased libido, insomnia, muscle spasms, muscle and bone pain, increased yawning and/or sneezing, myoclonus, lacrimation, , fever, diarrhea, restlessness, anger, and sadness. This may lead to resumption of use.
Frequent use of high doses of kratom may cause tremors, anorexia, weight loss, , psychosis and other mental health conditions. Kratom use has a small but statistically significant association with externalizing mental health disorders. Kratom use may worsen existing mental health conditions. In case reports associating kratom use with psychosis, it remains unclear whether kratom use directly caused psychosis or simply unmasked the condition. Serious toxicity is relatively rare and generally appears at high doses or when kratom is used with other substances. Drug interaction may result when kratom is combined with Alcoholic drink, , , , caffeine, cocaine, yohimbine, or monoamine oxidase inhibitors (MAOIs). Rhabdomyolysis is one of the rare and serious complications of this herb at high dosage.
In July 2016, the Centers for Disease Control issued a report stating that between 2010 and 2015, US poison control centers received 660 reports of exposure to kratom. Medical outcomes associated with kratom exposure were reported as minor (minimal signs or symptoms, which resolved rapidly with no residual disability) for 162 (24.5%) exposures, moderate (non-life-threatening, with no residual disability, but requiring some form of treatment) for 275 (41.7%) exposures, and major (life-threatening signs or symptoms, with some residual disability) for 49 (7.4%) exposures. Overall, 92.6% of outcomes were resolved with no residual disability. One death was reported in a person who was exposed to the medications paroxetine (an antidepressant) and lamotrigine (an anticonvulsant and mood stabilizer) in addition to kratom. For 173 (26.2%) exposure calls, no effects were reported, or poison center staff members were unable to follow up regarding effects.
A 2019 report from the American Association of Poison Control Centers (AAPCC) noted that kratom use was increasing rapidly, with 1807 kratom exposures and a 52-fold increase occurring over the years 2011 to 2017. Most exposures occurred intentionally by adult males in their homes, with 32% of the incidents requiring admission to a health care facility and half of the admissions as a serious medical condition. Multiple-substance exposures were associated with a higher number of hospitalizations than kratom-only exposures and involved 11 deaths, including two due to kratom alone. Post-mortem toxicology testing detected multiple substances for almost all those who died, with fentanyl and fentanyl analogs being the most frequently identified co-occurring substances.
Overdoses of kratom are managed similarly to , and naloxone can be considered to treat an overdose that results in a reduced impulse to breathe, despite mixed results for its utility, based on animal models.
From October 2017 to February 2018 in the United States, 28 people in 20 different states were infected with salmonella, an outbreak linked to the consumption of contaminated pills, powder, tea, or unidentified sources of kratom. An analytical method using whole genome sequencing applied to samples from the infected users indicated that the salmonella outbreak likely had a common kratom source.
Over 18 months in 2016 and 2017, 152 overdose deaths involving kratom were reported in the United States, with kratom as the primary overdose agent in 91 of the deaths, and 7 with kratom being the only agent detected. Nine deaths occurred in Sweden during 2010–11 relating to use of Krypton, a mixture of kratom, caffeine and O-desmethyltramadol, a metabolite of the opioid analgesic tramadol.
Kratom contains at least 54 . These include mitragynine, 7-hydroxymitragynine (7-HMG), speciociliatine, paynantheine, corynantheidine, speciogynine, mitraphylline, rhynchophylline, mitralactonal, Ajmalicine, and mitragynaline. The alkaloids mitragynine and 7-hydroxymitragynine are responsible for many of the complex effects of kratom, but other alkaloids may also contribute Drug synergy.
The effects of both mitragynine and 7-HMG remain disputed despite substantial study. Both are of the μ-opioid receptor. While most data indicates agonism at all three opioid receptors, other data suggests the alkaloids are antagonists of the δ-opioid receptor with low affinity for the κ-opioid receptor. 7-HMG appears to have higher affinity at the μ-opioid receptor than mitragynine. These compounds display functional selectivity and do not activate the Arrestin pathway partly responsible for the respiratory depression, constipation, and sedation associated with traditional . Both mitragynine and 7-HMG readily cross the blood-brain barrier.
Mitragynine also appears to inhibit COX-2, block L-type and T-type calcium channels, and interact with other receptors in the brain including 5-HT2C and 5-HT7 serotonin receptors, D2 dopamine receptors, and A2A adenosine receptors. Mitragynine stimulates α2-adrenergic receptors, inhibiting the release of norepinephrine (noradrenaline); other compounds in this class include dexmedetomidine, which is used for sedation, and clonidine, which is used to manage anxiety and some symptoms of opioid withdrawal. This activity might explain why kratom can be dangerous when used in combination with other sedatives. Kratom also contains rhynchophylline, a non-competitive NMDA receptor antagonist.
Mitragynine is metabolism in humans via phase I and phase II mechanisms with the resulting excreted in urine. In in vitro experiments, kratom extracts enzyme inhibitor CYP3A4, CYP2D6, and CYP1A2 , which results in significant potential for .
In addition to , M. speciosa produces many other secondary metabolites. These include various , and other Monoterpene, Triterpene such as ursolic acid and Oleanolic acid, as well as various including the apigenin and quercetin. Although some of these compounds possess Analgesic, anti-inflammatory, gastrointestinal, antidepressant, antioxidant, and Antibiotic effects in cells and non-human animals, there is no sufficient evidence to support the clinical use of kratom in humans.
In 2021, the World Health Organization's Executive Committee on Drug Dependency investigated the risks of kratom and declined to recommend a critical review of it. The committee, however, recommended kratom be kept "under surveillance."
In Bulgaria and Norway, kratom is a controlled substance.
In the Czech Republic, regulated sales of kratom and kratom extracts became legal starting in July 2025.
In Finland, scheduled in the "government decree on psychoactive substances banned from the consumer market".
In the Republic of Ireland in 2017, kratom was designated a Schedule 1 illegal drug (the highest level), under the names 7-hydroxymitragynine and mitragynine.
In the UK, the sale, import, and export of kratom is prohibited under the Psychoactive Substances Act 2016, which broadly bans any substance that "produces a psychoactive effect".
Argentina banned Kratom in 2017.
Brazil listed kratom as a New Psychoactive Substance (NPS) in 2020. However, it remains legal until it is included among prohibited substances. Kratom Legality by Country 2025
The Thai government has considered legalizing kratom for recreational use in 2004, 2009, 2013, and 2020. In 2018, Thailand became the first Southeast Asian country to legalize kratom for medical purposes. In 2021, Thailand fully legalized kratom and removed it from the list of Category V narcotics, and more than 12,000 people who had been convicted for kratom-related offences when it was still considered a narcotic were granted an amnesty.
On August 13, 2025, Florida attorney general James Uthmeier announced an emergency rule placing 7-hydroxymitragynine into Schedule I status under Florida state law, without any mention of a carve out or any exclusions for Mitragyna speciosa which contains low amounts of 7OH, effectively making kratom illegal in Florida.
In February 2018, the commissioner of the FDA, Scott Gottlieb, released a statement describing further opioid-like properties of kratom and stating that it should not be used for any medical treatment or recreational use. Also in 2018, the FDA supervised the voluntary destruction of kratom dietary supplements by a nationwide distributor in Missouri, and encouraged all companies involved in kratom commerce to remove their products from the market. On February 26, the FDA warned a California manufacturer of a kratom product called "Mitrasafe" that the supplement was not confirmed as safe, was not approved as a dietary supplement or drug, and was illegal for interstate commerce.
Although it was a federally legal dietary supplement, kratom was not approved as a therapeutic agent in the United States due to the poor quality of the research. In November 2017, the FDA cited serious concerns over the marketing and effects (including death) associated with the use of kratom in the United States, stating that "There is no reliable evidence to support the use of kratom as a treatment for opioid use disorder; there are currently no FDA-approved therapeutic uses of kratom... and the FDA has evidence to show that there are significant safety issues associated with its use."
The DEA noted the responses but said that it intended to go forward with the listing; a spokesman said: "We can't rely upon public opinion and anecdotal evidence. We have to rely upon science." In October 2016, the DEA withdrew its notice of intent while inviting public comments over a review period ending on December 1, 2016. As of July 2016, Alabama, Arkansas, Indiana, Vermont, and Wisconsin had made kratom illegal, and the US Army had forbidden soldiers from using it. Between February 2014 and July 2016, U.S. law-enforcement authorities "encountered 55 tons of kratom," or roughly "50 million individual doses," according to the International Narcotics Control Board.
Kratom use has not been shown to affect positive mental health and shows a very small association with negative indicators (mainly externalizing disorders).
Description
Uses of the leaves
Traditional use
Opioid withdrawal
Recreational use
Adverse effects
Addiction
Respiratory depression
Liver toxicity
Death
Pharmacology
+ Mitragyna speciosa alkaloids at opioid receptors
Chemistry
Detection in body fluids
Regulation
ASEAN
Australia and New Zealand
Canada
Europe
South America
Indonesia
Malaysia
Thailand
United States
FDA assessment
DEA scheduling
Public response
Research directions
See also
External links
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