Kratom (Mitragynine): general

Kratom is a tree in the coffee family native to Southeast Asia, and mitragynine — the plant's main active alkaloid — is extracted from its leaves [1]. It's typically taken as a tea or a powder [2]. Mitragynine and a related compound, 7-hydroxymitragynine, are partial agonists at the µ-opioid receptor, the same receptor site targeted by opioids like morphine [3][4]. This is why kratom's effects have been described as similar to both opioids and stimulants [2]. Mitragynine also binds to adrenergic, serotonergic, and dopamine receptors, which may account for some of the breadth of effects people report [3].

As with opioids generally, the receptors involved send signals that keep breathing going, and binding at those receptors can interrupt that signal [5]. There is no reliable dosing, onset, or duration information here to guide a first use — if you're going ahead anyway, that absence is itself the reason to start far lower than feels sensible, and not alone.

Kratom has a long history as a folk remedy for pain, anxiety, and depression, and among laborers in rural Southeast Asia for pain relief and fatigue [6][2]. It's also been used traditionally, and researched, as a way to manage opioid withdrawal symptoms [2][4]. None of this makes it a substitute for medical treatment, and the WHO's expert committee has said there isn't yet enough evidence to warrant a full critical review of mitragynine or 7-hydroxymitragynine [3]. Legal status differs sharply between countries, partly over concern about dependence [6].

References

1. The Chemical and Pharmacological Properties of Mitragynine and Its Diastereomers: An Insight Review — Frontiers in Pharmacology
2. Kratom — StatPearls (NCBI Bookshelf)
3. Kratom, mitragynine, 7-hydroxymitragynine — WHO Expert Committee on Drug Dependence (ECDD) Information Repository
4. Mitragynine — Wikipedia
5. Opioid Overdose: Signs, Symptoms & Treatment — Cleveland Clinic
6. Mitragynine | Ligand page — IUPHAR/BPS Guide to PHARMACOLOGY