Mitragynine is an indole alkaloid from the plant Mitragyna speciosa (Kratom). It has stimulatory, antinociceptive, and opiate-like effects, acting through noradrenergic, serotonergic, and opioid receptors.
Traditionally, fresh or dried kratom leaves are chewed or made into tea; they are seldom smoked. At a low dose, kratom has stimulant effects and is used to combat fatigue during long working hours. At high dosages, however, it can have sedative-narcotic effects. It is also used in traditional medicine and as an opium substitute.