Mitragyna speciosa

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. Kratom has opioid-like properties and some stimulant-like effects.

The efficacy and safety of kratom are unclear. In 2019, the United States 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 50 alkaloids—primarily mitragynine and 7-hydroxymitragynine—which act as partial agonists at μ-opioid receptors with complex, receptor-specific effects and additional interactions across various neural pathways, contributing to both therapeutic potential and safety concerns.

Anecdotal reports describe increased alertness, physical energy, talkativeness, sociability, sedation, changes in mood, and pain relief following kratom use at various doses. Common side-effects include appetite loss, erectile dysfunction, nausea and constipation. More severe side-effects may include respiratory depression (decreased breathing), seizure, psychosis, elevated heart rate and blood pressure, trouble sleeping, and liver injury. Addiction is a possible risk with regular use: when use is stopped, withdrawal symptoms may occur. A number of deaths have been connected to the use of kratom, both by itself and mixed with other substances. Serious toxicity is relatively rare and generally appears at high doses or when kratom is used with other substances.

As of 2018, kratom is a controlled substance in 16 countries. Some countries, like Indonesia and Thailand, have recently moved toward regulated legal production or 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.