Mitragynine

Mitragynine at a Glance

Mitragynine is the principal alkaloid of kratom (Mitragyna speciosa), a Southeast Asian tree in the coffee family. It makes up roughly two-thirds of the leaf’s total alkaloid fraction and between about 0.7% and 4.9% of dry leaf weight, varying several-fold with genotype, season and provenance ^{42,44Reference 42Sengnon N et al. · 2023Seasonal and Geographic Variation in Alkaloid Content of Kratom (Mitragyna speciosa (Korth.) Havil.) from Thailand — analyticalView study →Reference 44Ransden KE et al. · 2026Comparative analysis of monoterpene indole alkaloid composition and genotypic variation in Thai Mitragyna speciosa — analyticalView study →}. It is the molecule that makes kratom pharmacologically unusual — and the one that makes kratom hard to classify.

Structurally it is a corynanthe-type monoterpene indole alkaloid (systematically 9-methoxycorynantheidine), built on a tryptamine-derived skeleton. It has no structural relationship to morphine: it is not a morphinan, and molecular docking suggests it adopts a binding pose at the mu-opioid receptor that differs from that of classical opioids ^{1Reference 1Kruegel AC et al. · 2016Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor ModulatorsView study →}. Functionally it behaves as a low-efficacy, G-protein-biased partial agonist at the human mu-opioid receptor with little or no β-arrestin recruitment, alongside meaningful non-opioid activity at adrenergic and serotonergic targets ^{1,11,14Reference 1Kruegel AC et al. · 2016Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor ModulatorsView study →Reference 11Obeng S et al. · 2020Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom AlkaloidsView study →Reference 14Matsumoto K et al. · 1997AnimalSuppressive effect of mitragynine on the 5-methoxy-N,N-dimethyltryptamine-induced head-twitch response in mice — animal modelView study →}.

The single most important fact about mitragynine is metabolic. It is oxidised by CYP3A4 to 7-hydroxymitragynine, a far more potent and more efficacious mu-agonist, and there is a serious, well-evidenced argument that much of mitragynine’s opioid effect in vivo is really its metabolite’s — that mitragynine functions partly as a prodrug ^{3,5,6Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →Reference 5Chakraborty S et al. · 2021Oxidative Metabolism as a Modulator of Kratom’s Biological ActionsView study →Reference 6Kamble SH et al. · 2019Metabolite profiling and identification of enzymes responsible for the metabolism of mitragynine, the major alkaloid of Mitragyna speciosa (kratom)View study →}. That argument, and the limits of it, are the spine of the whole account.

This is a scholarly pharmacology, toxicology, forensic and legal-status reference. It gives no dose for effect, no preparation, extraction or potentiation guidance, and no advice about use. It states the dependence liability, the hepatotoxicity signal and the forensic mortality data plainly, and is equally plain about how heavily confounded the harm data are.

The Biased-Agonism Argument, and Its Limits

The mechanistic story that made mitragynine famous runs like this. Classical opioid agonists activate the mu-opioid receptor through two downstream arms: G-protein signalling (associated with analgesia) and β-arrestin recruitment (historically associated with respiratory depression, constipation and tolerance). In the first receptor-level functional characterisation of the Mitragyna alkaloids at the human mu-, kappa- and delta-opioid receptors, Kruegel and colleagues found that mitragynine and 7-hydroxymitragynine are partial agonists at mu, competitive antagonists at kappa and delta, and G-protein-biased — they do not recruit β-arrestin following receptor activation ^{1Reference 1Kruegel AC et al. · 2016Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor ModulatorsView study →}. If β-arrestin drives respiratory depression, a G-protein-biased mu-agonist should in principle deliver analgesia with a wider safety margin.

Three things should be held against that story.

1. The β-arrestin hypothesis itself has weakened badly. The foundational claim was tested directly in mice engineered without β-arrestin2 signalling at the mu receptor, and morphine-induced respiratory depression persisted — the effect is not β-arrestin-dependent ^{49Reference 49Kliewer A et al. · 2020AnimalMorphine-induced respiratory depression is independent of β-arrestin2 signalling — mouse genetic modelView study →}. A competing explanation emerged: what looks like “bias” in many biased-agonist candidates is better explained by low intrinsic efficacy for G-protein activation, which shifts the whole dose–response for every mu-mediated effect rather than separating good effects from bad ^{47Reference 47Gillis A et al. · 2020Low intrinsic efficacy for G protein activation can explain the improved side effect profiles of new opioid agonistsView study →}. That reframing has itself been contested — a subsequent analysis argued low intrinsic efficacy alone cannot account for the improved side-effect profiles reported for these agonists ^{48Reference 48Stahl EL · 2022Low Intrinsic Efficacy Alone Cannot Explain the Improved Side Effect Profiles of New Opioid AgonistsView study →}. The honest position is that biased agonism is an unsettled field, and the “safer opioid” inference drawn from it has not held up well.

2. Mitragynine’s own mu efficacy is disputed at the bench. A careful side-by-side comparison using [³⁵S]GTPγS stimulation at the mu receptor found mitragynine behaving as an antagonist, not an agonist, while 7-hydroxymitragynine was a partial agonist with an Emax of about 41% ^{2Reference 2Obeng S et al. · 2021In vitroPharmacological Comparison of Mitragynine and 7-Hydroxymitragynine: In Vitro Affinity and Efficacy for μ-Opioid Receptor and Opioid-Like Behavioral Effects in RatsView study →}. In the same study 7-hydroxymitragynine had roughly nine-fold higher mu affinity than mitragynine, produced antinociception where mitragynine did not, and mitragynine actually decreased morphine antinociception while increasing the potency of morphine’s discriminative-stimulus effects ^{2Reference 2Obeng S et al. · 2021In vitroPharmacological Comparison of Mitragynine and 7-Hydroxymitragynine: In Vitro Affinity and Efficacy for μ-Opioid Receptor and Opioid-Like Behavioral Effects in RatsView study →}. (The paper carries a published erratum affecting its reported binding constants, so the numerical affinities should be read from the corrected version; the qualitative direction — 7-hydroxymitragynine substantially higher in both affinity and efficacy — is not in dispute.) The reasonable synthesis is that mitragynine is a very low-efficacy mu ligand whose behaviour flips between “weak partial agonist” and “antagonist” depending on assay, receptor reserve and system.

3. Whatever bias exists may be moot if the metabolite is doing the work. See the next section.

What is robust is the observation that respiratory depression by mitragynine hits a ceiling. In freely moving mice, oral mitragynine produced no further respiratory depression above about 10 mg/kg, whereas 7-hydroxymitragynine was dose-dependent throughout; inhibiting CYP3A reduced mitragynine’s respiratory depression and antinociception without touching 7-hydroxymitragynine’s ^{4Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →}. The authors attribute the ceiling not to receptor bias but to metabolic saturation — a rate limit on how fast mitragynine can be converted to its active metabolite ^{4Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →}. That is a mechanistically different, and better-supported, explanation for the same clinical impression.

The Metabolite Question: Is Mitragynine a Prodrug?

This is the central unresolved issue in mitragynine pharmacology, and it is worth stating both sides.

The prodrug case. Mitragynine is converted, in both mouse and human liver preparations, to the much more potent mu-agonist 7-hydroxymitragynine, and the conversion is mediated by CYP3A isoforms ^{3,6Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →Reference 6Kamble SH et al. · 2019Metabolite profiling and identification of enzymes responsible for the metabolism of mitragynine, the major alkaloid of Mitragyna speciosa (kratom)View study →}. In mice, 7-hydroxymitragynine formed from administered mitragynine reaches brain concentrations sufficient to explain most or all of the opioid-receptor-mediated analgesic activity attributed to mitragynine ^{3Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →}. At the same time, mitragynine itself accumulates in brain at concentrations very high relative to its own mu binding affinity without producing the expected effect — which is what you would see if it were not directly activating the receptor ^{3Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →}. Blocking CYP3A abolishes much of mitragynine’s antinociception and respiratory depression while leaving 7-hydroxymitragynine’s intact ^{4Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →}. And the in vitro efficacy comparison finds mitragynine an antagonist and only the metabolite an agonist ^{2Reference 2Obeng S et al. · 2021In vitroPharmacological Comparison of Mitragynine and 7-Hydroxymitragynine: In Vitro Affinity and Efficacy for μ-Opioid Receptor and Opioid-Like Behavioral Effects in RatsView study →}. Taken together this is a strong metabolism-dependent mechanism, and it means route of administration matters enormously: parenteral mitragynine bypasses much of the first-pass conversion that oral exposure produces ^{3Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →}.

The case against a simple prodrug reading. Mitragynine has substantial pharmacology that 7-hydroxymitragynine cannot account for. It binds adrenergic receptors and, unlike its metabolite, produces effects that are only partly naltrexone-reversible — in drug-discrimination work, naltrexone antagonised mitragynine’s discriminative-stimulus effects but not its rate-decreasing effects ^{2,11Reference 2Obeng S et al. · 2021In vitroPharmacological Comparison of Mitragynine and 7-Hydroxymitragynine: In Vitro Affinity and Efficacy for μ-Opioid Receptor and Opioid-Like Behavioral Effects in RatsView study →Reference 11Obeng S et al. · 2020Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom AlkaloidsView study →}. Its behavioural profile in self-administration studies is the opposite of the metabolite’s: 7-hydroxymitragynine is readily self-administered by rats and carries clear reinforcing properties, while mitragynine shows limited abuse liability and reduces heroin self-administration ^{18,19Reference 18Yue K et al. · 2018AnimalAbuse liability of mitragynine assessed with a self-administration procedure in rats — animal modelView study →Reference 19Hemby SE et al. · 2019AnimalAbuse liability and therapeutic potential of the Mitragyna speciosa (kratom) alkaloids mitragynine and 7-hydroxymitragynine — rat self-administrationView study →}. And the metabolism does not stop at 7-hydroxymitragynine. CYP3A also drives a skeletal rearrangement to mitragynine-pseudoindoxyl, a multifunctional mu-agonist/delta–kappa-antagonist that is itself an active analgesic with an unusual receptor profile, while a non-CYP oxidation pathway yields 3-dehydromitragynine, flagged as potentially toxic ^{5,16Reference 5Chakraborty S et al. · 2021Oxidative Metabolism as a Modulator of Kratom’s Biological ActionsView study →Reference 16Váradi A et al. · 2016In vitroMitragynine/Corynantheidine Pseudoindoxyls As Opioid Analgesics with Mu Agonism and Delta Antagonism — in vitro / mouseView study →}. Human liver microsomes generate thirteen identified metabolites in total — four oxidative products and a 9-O-demethylated product dominating — with CYP3A4 predominant and minor contributions from CYP2D6 and CYP2C9 ^{6Reference 6Kamble SH et al. · 2019Metabolite profiling and identification of enzymes responsible for the metabolism of mitragynine, the major alkaloid of Mitragyna speciosa (kratom)View study →}.

Where that leaves it. The defensible statement is that mitragynine’s mu-opioid effects are largely metabolite-mediated, but mitragynine is not merely a prodrug — it is a parent molecule with its own non-opioid pharmacology whose oxidative metabolites collectively, not singly, produce the observed profile ^{5Reference 5Chakraborty S et al. · 2021Oxidative Metabolism as a Modulator of Kratom’s Biological ActionsView study →}. Two practical consequences follow. First, CYP3A activity becomes a determinant of effect: anything that induces or inhibits CYP3A shifts the balance between parent and metabolite. Second, commercial products that add concentrated or semi-synthetic 7-hydroxymitragynine are not “stronger kratom” — they deliver a pharmacologically different, more efficacious and more reinforcing agonist, bypassing the metabolic rate limit that produces the ceiling effect ^{40,41Reference 40Gour A et al. · 2026Mislabeling and Status of Semisynthetic Kratom-Derived Products in the US Market — analyticalView study →Reference 41Gour A et al. · 2025ReviewFrom Kratom to Semi-Synthetic Opioids: The Rise and Risks of MGM-15 — analytical reviewView study →}.

Non-Opioid Pharmacology

Framing mitragynine as “an opioid” understates it. The molecule is genuinely polypharmacological, and the non-opioid targets are what shape kratom’s atypical reported profile — stimulant-like at low exposure, sedative and analgesic at higher exposure.

Adrenergic. Mitragynine binds α-adrenergic receptors, though with lower affinity than at opioid receptors — the reverse of its sibling corynantheidine, which favours adrenergic over opioid targets ^{11Reference 11Obeng S et al. · 2020Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom AlkaloidsView study →}. α₂-adrenergic activity is mechanistically interesting because α₂-agonists (clonidine, lofexidine) are established treatments for opioid-withdrawal symptoms, which offers a non-opioid route by which kratom alkaloids might blunt withdrawal ^{11,50Reference 11Obeng S et al. · 2020Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom AlkaloidsView study →Reference 50Hiranita T et al. · 2022In vitroIn vitro and in vivo pharmacology of kratom — reviewView study →}.

Serotonergic. Mitragynine suppresses the 5-methoxy-N,N-dimethyltryptamine-induced head-twitch response in mice, a classic 5-HT2A-mediated behaviour — evidence of 5-HT2A antagonism ^{14Reference 14Matsumoto K et al. · 1997AnimalSuppressive effect of mitragynine on the 5-methoxy-N,N-dimethyltryptamine-induced head-twitch response in mice — animal modelView study →}. Serotonergic activity is repeatedly invoked to explain the mood-related effects reported by users, but the receptor-level work behind it is thin and mostly old.

Supraspinal opioid action. The earliest mechanistic animal work established that mitragynine’s antinociception involves supraspinal opioid receptors, with subsequent work identifying the receptor subtypes engaged ^{12,13Reference 12Matsumoto K et al. · 1996AnimalAntinociceptive action of mitragynine in mice: evidence for the involvement of supraspinal opioid receptors — animal modelView study →Reference 13Thongpradichote S et al. · 1998AnimalIdentification of opioid receptor subtypes in antinociceptive actions of supraspinally-administered mitragynine in mice — animal modelView study →}. This predates the metabolite discovery, and in hindsight much of it is compatible with metabolite-mediated action.

The biphasic framing. The “stimulant at low exposure, sedative and analgesic at higher exposure” description entered the modern literature through early pharmacology reviews and has been carried forward largely on the strength of user report rather than controlled dose–response work ^{57Reference 57Prozialeck WC et al. · 2012ReviewPharmacology of kratom: an emerging botanical agent with stimulant, analgesic and opioid-like effects — reviewView study →}. It remains the standard clinical-pharmacology summary of the leaf ^{55Reference 55Hartley C 2nd et al. · 2022ReviewClinical Pharmacology of the Dietary Supplement Kratom (Mitragyna speciosa) — reviewView study →}.

The polypharmacology argument. Reviews synthesising the last decade of work conclude that kratom is more accurately described as a substance with diverse and complex pharmacology than as a simple opioid, and that the popular framing as “an opioid” drives both regulatory and clinical misjudgements ^{37,50,56Reference 37Henningfield JE et al. · 2024ReviewKratom safety and toxicology in the public health context: research needs to better inform regulation — review (author conflicts of interest declared)View study →Reference 50Hiranita T et al. · 2022In vitroIn vitro and in vivo pharmacology of kratom — reviewView study →Reference 56Kruegel AC · 2018ReviewThe medicinal chemistry and neuropharmacology of kratom: A preliminary discussion of a promising medicinal plant and analysis of its potential for abuse — reviewView study →}.

What It's Used For

The evidence base is lopsided: extensive receptor pharmacology and rodent work on the isolated molecule, a large observational and survey literature on the whole leaf, and a very small number of controlled human studies — none of which tested isolated mitragynine.

Evidence by IndicationStrength of support · Beta

Support is an experimental score — weighted by study type (human > animal > in vitro) and volume — and here it reflects how well characterised an action is, not an endorsement or a recommendation. No isolated mitragynine has been tested for efficacy in a human trial; every human row rests on whole-leaf preparations.

01Analgesia (Metabolite-Dependent)Promising62%One human RCT on kratom decoction + extensive rodent antinociception; mechanism is largely 7-hydroxymitragynine-mediated ^{3,20Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →Reference 20Vicknasingam B et al. · 2020RCTKratom and Pain Tolerance: A Randomized, Placebo-Controlled, Double-Blind Study — randomised controlled trialView study →}

02Opioid-Withdrawal Self-ManagementPromising48%Consistent survey/observational data + rodent withdrawal models; no efficacy RCT, and kratom itself produces dependence ^{26,29,17Reference 26Singh D et al. · 2014ObservationalKratom (Mitragyna speciosa) dependence, withdrawal symptoms and craving in regular users — observational cohortView study →Reference 29Smith KE et al. · 2024ReviewControversies in Assessment, Diagnosis, and Treatment of Kratom Use Disorder — reviewView study →Reference 17Wilson LL et al. · 2021AnimalKratom Alkaloids, Natural and Semi-Synthetic, Show Less Physical Dependence and Ameliorate Opioid Withdrawal — mouse animal modelView study →}

03Stimulant-Like Effects at Low ExposureShaky36%Adrenergic pharmacology + large user-survey consistency; one placebo-controlled abuse-potential trial found only modest dose-related subjective effects ^{11,21,22Reference 11Obeng S et al. · 2020Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom AlkaloidsView study →Reference 21Coe M et al. · 2026RCTAssessment of Abuse Potential-Related Effects of Oral Dried Kratom Leaf Powder in Healthy Normal Participants Following Single and Multiple Daily Doses — randomised placebo-controlled trialView study →Reference 22Grundmann O · 2017ObservationalPatterns of Kratom use and health impact in the US — Results from an online survey — observationalView study →}

04Antitussive & Antidiarrhoeal ActionsShaky22%Traditional use plus mu-mediated GI-transit inhibition in rodents; no controlled human data ^{5,15Reference 5Chakraborty S et al. · 2021Oxidative Metabolism as a Modulator of Kratom’s Biological ActionsView study →Reference 15Takayama H · 2004ReviewChemistry and pharmacology of analgesic indole alkaloids from the rubiaceous plant, Mitragyna speciosa — reviewView study →}

Mechanisms

The load-bearing point: the receptor pharmacology and the metabolic pharmacology are inseparable here. Mitragynine’s mu effects depend on a CYP3A step, and CYP3A is simultaneously the enzyme mitragynine inhibits — so exposure, effect and interaction risk are all coupled ^{3,4,8Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}.

Pharmacokinetics

Mitragynine is a lipophilic base with fast absorption and a long tail. The only human pharmacokinetic study — nine chronic users given controlled kratom tea after a seven-day steady-state run-in — found a Tmax of 0.83 ± 0.35 h, a terminal half-life of 23.2 ± 16.1 h (about a day, with wide inter-individual spread), and an apparent volume of distribution of 38.0 ± 24.3 L/kg, indicating extensive tissue distribution; pharmacokinetics were linear and fitted an oral two-compartment model ^{9Reference 9Trakulsrichai S et al. · 2015Pharmacokinetics of mitragynine in manView study →}. Only 0.14% of the dose was excreted unchanged in urine, so clearance is essentially all metabolic ^{9Reference 9Trakulsrichai S et al. · 2015Pharmacokinetics of mitragynine in manView study →}.

Metabolism is dominated by CYP3A4. Human liver microsome and S9 work identified thirteen metabolites, with four oxidative products and a 9-O-demethylated product as the majors; CYP3A4 predominates, with minor CYP2D6 and CYP2C9 contributions, and CYP3A4 specifically catalyses formation of 7-hydroxymitragynine ^{6Reference 6Kamble SH et al. · 2019Metabolite profiling and identification of enzymes responsible for the metabolism of mitragynine, the major alkaloid of Mitragyna speciosa (kratom)View study →}. Further oxidative chemistry yields mitragynine-pseudoindoxyl (CYP3A-mediated rearrangement) and 3-dehydromitragynine (non-CYP) ^{5Reference 5Chakraborty S et al. · 2021Oxidative Metabolism as a Modulator of Kratom’s Biological ActionsView study →}.

Two absorption details matter. Mitragynine is unstable in simulated gastric fluid (~26% degradation) but stable in simulated intestinal fluid; 7-hydroxymitragynine degrades ~27% in gastric fluid, with a substantial fraction (~23%) converting back to mitragynine — so the parent/metabolite ratio delivered is partly a function of gastric conditions ^{10Reference 10Manda VK et al. · 2014In vitroEvaluation of in vitro absorption, distribution, metabolism, and excretion (ADME) properties of mitragynine, 7-hydroxymitragynine, and mitraphyllineView study →}. P-glycoprotein interaction was also characterised in the same in-vitro ADME work ^{10Reference 10Manda VK et al. · 2014In vitroEvaluation of in vitro absorption, distribution, metabolism, and excretion (ADME) properties of mitragynine, 7-hydroxymitragynine, and mitraphyllineView study →}.

For forensic purposes, mitragynine shows modest postmortem redistribution (mean heart-to-femoral blood ratio 1.37) and is far more abundant than its metabolite in blood — mean mitragynine:7-hydroxymitragynine ratios of about 31 in femoral blood and 32 in heart blood, versus ~15–17 in vitreous humour and urine ^{34Reference 34Osawa KA · 2025Postmortem distribution of mitragynine and 7-hydroxymitragynine in 51 cases — forensic analyticalView study →}.

Clinical Trials

There are no trials of isolated mitragynine for any indication. The controlled human literature uses whole-leaf preparations: one randomised, placebo-controlled, double-blind pain-tolerance study in regular users ^{20Reference 20Vicknasingam B et al. · 2020RCTKratom and Pain Tolerance: A Randomized, Placebo-Controlled, Double-Blind Study — randomised controlled trialView study →}; one randomised, placebo-controlled abuse-potential study of dried leaf powder in 116 kratom-naive adults ^{21Reference 21Coe M et al. · 2026RCTAssessment of Abuse Potential-Related Effects of Oral Dried Kratom Leaf Powder in Healthy Normal Participants Following Single and Multiple Daily Doses — randomised placebo-controlled trialView study →}; and one clinical pharmacokinetic drug-interaction study with a CYP3A and CYP2D6 probe cocktail ^{8Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}. Research priorities identified in the regulatory-science literature include standardised products, dose–response characterisation and controlled withdrawal-treatment trials ^{37Reference 37Henningfield JE et al. · 2024ReviewKratom safety and toxicology in the public health context: research needs to better inform regulation — review (author conflicts of interest declared)View study →}.

Last checked: July 2026.

Isolate vs. Plant Studies

The split here is unusually clean, and it cuts against the isolate.

All the mechanism is isolate work. Receptor binding and functional assays, the metabolite discovery, the CYP inhibition profiling, the respiratory-ceiling experiments and the self-administration studies were all done with purified mitragynine (and purified 7-hydroxymitragynine) ^{1,2,3,4,7,18,19Reference 1Kruegel AC et al. · 2016Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor ModulatorsView study →Reference 2Obeng S et al. · 2021In vitroPharmacological Comparison of Mitragynine and 7-Hydroxymitragynine: In Vitro Affinity and Efficacy for μ-Opioid Receptor and Opioid-Like Behavioral Effects in RatsView study →Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →Reference 18Yue K et al. · 2018AnimalAbuse liability of mitragynine assessed with a self-administration procedure in rats — animal modelView study →Reference 19Hemby SE et al. · 2019AnimalAbuse liability and therapeutic potential of the Mitragyna speciosa (kratom) alkaloids mitragynine and 7-hydroxymitragynine — rat self-administrationView study →}. That is a genuine strength — the molecular pharmacology is not inferred from an extract.

All the human evidence is whole leaf. The pain-tolerance RCT used a kratom decoction, the abuse-potential trial used dried leaf powder, the pharmacokinetic study used kratom tea, and the drug-interaction study used 2 g of tea ^{8,9,20,21Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →Reference 9Trakulsrichai S et al. · 2015Pharmacokinetics of mitragynine in manView study →Reference 20Vicknasingam B et al. · 2020RCTKratom and Pain Tolerance: A Randomized, Placebo-Controlled, Double-Blind Study — randomised controlled trialView study →Reference 21Coe M et al. · 2026RCTAssessment of Abuse Potential-Related Effects of Oral Dried Kratom Leaf Powder in Healthy Normal Participants Following Single and Multiple Daily Doses — randomised placebo-controlled trialView study →}. No human has been given isolated mitragynine in a published controlled trial. Every statement about what mitragynine does in people is therefore an inference from leaf exposure plus rodent pharmacology.

The transfer between the two is worse than usual, for three reasons. First, alkaloid content varies several-fold between leaf samples by genotype, season and provenance, so “grams of leaf” is a poor proxy for “milligrams of alkaloid” ^{42,44Reference 42Sengnon N et al. · 2023Seasonal and Geographic Variation in Alkaloid Content of Kratom (Mitragyna speciosa (Korth.) Havil.) from Thailand — analyticalView study →Reference 44Ransden KE et al. · 2026Comparative analysis of monoterpene indole alkaloid composition and genotypic variation in Thai Mitragyna speciosa — analyticalView study →}. Second, commercial products are frequently mislabelled, containing unreported alkaloids or lacking listed ones, and some contain concentrated 7-hydroxymitragynine or the potent semi-synthetic MGM-15 ^{40,41Reference 40Gour A et al. · 2026Mislabeling and Status of Semisynthetic Kratom-Derived Products in the US Market — analyticalView study →Reference 41Gour A et al. · 2025ReviewFrom Kratom to Semi-Synthetic Opioids: The Rise and Risks of MGM-15 — analytical reviewView study →}. Third, the leaf contains a substantial cast of other alkaloids — paynantheine, speciogynine, speciociliatine, corynantheidine, 9-hydroxycorynantheidine, mitraversine and the oxindoles mitraphylline, rhynchophylline and isorhynchophylline — several of which have their own receptor and CYP activity ^{7,11,51Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →Reference 11Obeng S et al. · 2020Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom AlkaloidsView study →Reference 51Kamble SH et al. · 2022Metabolism of Speciociliatine, an Overlooked Kratom Alkaloid for its Potential Pharmacological EffectsView study →}. Corynantheidine is a mu-antagonist and favours adrenergic over opioid binding, so the leaf is not simply “dilute mitragynine” ^{11Reference 11Obeng S et al. · 2020Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom AlkaloidsView study →}.

Who Funds the Kratom Literature

This deserves stating because it is unusual in a phytochemistry page, and because it changes how the safety literature should be read.

The kratom evidence base is substantially populated by authors with declared commercial or litigation ties on both sides of the argument. The most-cited recent regulatory-science synthesis was written by authors who consult, through a scientific-affairs firm, for kratom trade bodies and product sponsors, and several are paid expert witnesses in kratom litigation ^{37Reference 37Henningfield JE et al. · 2024ReviewKratom safety and toxicology in the public health context: research needs to better inform regulation — review (author conflicts of interest declared)View study →}. The randomised abuse-potential trial was sponsored by a kratom product company whose consultants are among the authors ^{21Reference 21Coe M et al. · 2026RCTAssessment of Abuse Potential-Related Effects of Oral Dried Kratom Leaf Powder in Healthy Normal Participants Following Single and Multiple Daily Doses — randomised placebo-controlled trialView study →}. Conversely, the systematic evaluation arguing that case reports are too confounded to attribute harm to kratom was produced by a consultancy whose scientific group has been engaged by kratom processors and distributors in litigation and advisory roles ^{36Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →}.

None of this makes any of those papers wrong — they are peer-reviewed, their conflict statements are complete and explicit, and the underlying data are real. But it means the two loudest interpretive positions in the field (“kratom is a mischaracterised botanical” and “kratom deaths are polydrug artefacts”) both come predominantly from commercially engaged sources. The independent-source spine is deliberately the academic pharmacology ^{1,2,3,4,5,6,7Reference 1Kruegel AC et al. · 2016Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor ModulatorsView study →Reference 2Obeng S et al. · 2021In vitroPharmacological Comparison of Mitragynine and 7-Hydroxymitragynine: In Vitro Affinity and Efficacy for μ-Opioid Receptor and Opioid-Like Behavioral Effects in RatsView study →Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →Reference 5Chakraborty S et al. · 2021Oxidative Metabolism as a Modulator of Kratom’s Biological ActionsView study →Reference 6Kamble SH et al. · 2019Metabolite profiling and identification of enzymes responsible for the metabolism of mitragynine, the major alkaloid of Mitragyna speciosa (kratom)View study →Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →}, the university-run clinical interaction study ^{8Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}, the Southeast Asian user cohorts ^{26,27,28Reference 26Singh D et al. · 2014ObservationalKratom (Mitragyna speciosa) dependence, withdrawal symptoms and craving in regular users — observational cohortView study →Reference 27Singh D et al. · 2018ObservationalSeverity of Kratom (Mitragyna speciosa Korth.) Psychological Withdrawal Symptoms — observationalView study →Reference 28Singh D et al. · 2019ObservationalLong-Term Cognitive Effects of Kratom (Mitragyna speciosa Korth.) Use — observationalView study →}, the DILIN hepatotoxicity network ^{30Reference 30Ahmad J et al. · 2021ObservationalLiver injury associated with kratom, a popular opioid-like product: Experience from the U.S. drug induced liver injury network — observational cohortView study →}, and the medical-examiner casework ^{33,34,35,53Reference 33Behonick GS et al. · 2022Case reportTwo Single-Drug Fatal Intoxications by Mitragynine — case reportView study →Reference 34Osawa KA · 2025Postmortem distribution of mitragynine and 7-hydroxymitragynine in 51 cases — forensic analyticalView study →Reference 35Iuteri CM et al. · 2026ObservationalCase-control study of mitragynine deaths in Florida — case-controlView study →Reference 53Kliewer RS et al. · 2026Determination of mitragynine concentrations in medicolegal death investigations at the Oklahoma Office of the Chief Medical Examiner — forensic analyticalView study →}.

Drug Interactions: CYP2D6 & CYP3A4

Mitragynine has one of the more concrete interaction profiles of any plant alkaloid here, because it has been characterised both in vitro and in a controlled human study.

CYP2D6 — potent inhibition in vitro. Screening major kratom alkaloids against human liver microsomes, mitragynine and corynantheidine were potent CYP2D6 inhibitors (IC50 2.2 and 4.2 µM), both competitive, with Ki values of 1.1 and 2.8 µM; speciogynine and paynantheine showed moderate CYP2D6 inhibition ^{7Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →}. Since CYP2D6 handles a large share of psychiatric, cardiovascular and analgesic drugs — and converts codeine and tramadol to their active metabolites — this is a plausible route to clinically significant interactions ^{7Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →}.

CYP3A — time-dependent inhibition, demonstrated in humans. In 12 healthy adults, a single low dose of kratom tea (2 g) increased midazolam AUC 1.39-fold and Cmax 1.50-fold while leaving the half-life unchanged, a pattern indicating inhibition of intestinal rather than hepatic CYP3A ^{8Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}. A physiologically based pharmacokinetic model reproduced the effect using mitragynine as a time-dependent CYP3A inhibitor (KI ~4 µM, kinact ~0.07 min⁻¹) ^{8Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}. Isoform work adds a wrinkle: CYP3A4/5 inhibition by mitragynine and its siblings was substrate-dependent — visible with midazolam but not with testosterone as probe ^{7Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →}.

The unresolved discrepancy. In the same clinical study, the CYP2D6 probe dextromethorphan was unaffected (AUC ratio 0.99) despite mitragynine’s potent in vitro CYP2D6 inhibition ^{7,8Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}. The most likely explanation is exposure — a single 2 g tea dose is far below what regular users consume, and far below the concentrations at which the in vitro inhibition operates. The absence of an interaction at a low single dose is not evidence of safety at habitual exposure, and this is the single most important caveat in the interaction literature.

The reflexive interaction. Because mitragynine’s own activation to 7-hydroxymitragynine is CYP3A-mediated, CYP3A inhibitors should reduce its opioid effect and CYP3A inducers should increase the parent/metabolite ratio — a prediction directly confirmed in mice, where ketoconazole reduced mitragynine-induced antinociception and respiratory depression ^{4Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →}. Mitragynine therefore modulates the enzyme that activates it.

Dependence & Withdrawal

Physical dependence on kratom is not in serious doubt. A cohort study of regular long-term users in Malaysia documented tolerance, a withdrawal syndrome and craving, and a follow-up characterised the severity of the psychological withdrawal symptoms specifically ^{26,27Reference 26Singh D et al. · 2014ObservationalKratom (Mitragyna speciosa) dependence, withdrawal symptoms and craving in regular users — observational cohortView study →Reference 27Singh D et al. · 2018ObservationalSeverity of Kratom (Mitragyna speciosa Korth.) Psychological Withdrawal Symptoms — observationalView study →}. Withdrawal features reported across this literature are opioid-like — musculoskeletal pain, insomnia, irritability, rhinorrhoea, anxiety — and are the reason kratom is described as substituting one dependence for another rather than resolving one. A separate assessment of long-term users found no evidence of gross cognitive impairment attributable to regular use ^{28Reference 28Singh D et al. · 2019ObservationalLong-Term Cognitive Effects of Kratom (Mitragyna speciosa Korth.) Use — observationalView study →}.

The alkaloid-level picture is more nuanced, and it is the metabolite that carries the reinforcement. In rat self-administration, 7-hydroxymitragynine is self-administered and reinforcing, while mitragynine is not — mitragynine showed limited abuse liability and actually reduced heroin self-administration ^{18,19Reference 18Yue K et al. · 2018AnimalAbuse liability of mitragynine assessed with a self-administration procedure in rats — animal modelView study →Reference 19Hemby SE et al. · 2019AnimalAbuse liability and therapeutic potential of the Mitragyna speciosa (kratom) alkaloids mitragynine and 7-hydroxymitragynine — rat self-administrationView study →}. Rodent work comparing natural and semi-synthetic kratom alkaloids similarly found less physical dependence than with classical opioids, alongside amelioration of opioid withdrawal ^{17Reference 17Wilson LL et al. · 2021AnimalKratom Alkaloids, Natural and Semi-Synthetic, Show Less Physical Dependence and Ameliorate Opioid Withdrawal — mouse animal modelView study →}. In humans, the abuse-potential trial in kratom-naive adults found modest, dose-related subjective effects that decreased with 15 days of repeated dosing, and no participant reached the threshold for clinically meaningful opioid withdrawal on standard scales ^{21Reference 21Coe M et al. · 2026RCTAssessment of Abuse Potential-Related Effects of Oral Dried Kratom Leaf Powder in Healthy Normal Participants Following Single and Multiple Daily Doses — randomised placebo-controlled trialView study →}.

How to reconcile those. The cohort evidence describes people using leaf, often for years, at exposures far above anything a 15-day trial administers; the trial describes short-term, controlled, low exposure in naive subjects. Both can be true. Clinical reviews describe kratom use disorder as a real presentation whose assessment, diagnostic criteria and treatment remain genuinely contested ^{29Reference 29Smith KE et al. · 2024ReviewControversies in Assessment, Diagnosis, and Treatment of Kratom Use Disorder — reviewView study →}, and note that dependence and toxicity vary sharply with product type — concentrated extracts and 7-hydroxymitragynine-enriched products behaving very differently from traditional leaf ^{52Reference 52Vadiei N et al. · 2025ReviewThe Impact of Diverse Kratom Products on Use Patterns, Dependence, and Toxicity — reviewView study →}.

Toxicology & the Death-Data Problem

Hepatotoxicity. The clearest organ signal. The US Drug-Induced Liver Injury Network prospectively identified kratom-associated liver injury, typically with a cholestatic or mixed pattern, presenting within weeks of starting use ^{30Reference 30Ahmad J et al. · 2021ObservationalLiver injury associated with kratom, a popular opioid-like product: Experience from the U.S. drug induced liver injury network — observational cohortView study →}; individual case reports describe the same picture with conservative recovery on withdrawal ^{31Reference 31Fernandes CT et al. · 2019Case reportKratom-Induced Cholestatic Liver Injury and Its Conservative Management — case reportView study →}. The incidence is unknown and the mechanism is uncharacterised — it is not known whether mitragynine, a metabolite, another alkaloid, or a product contaminant is responsible.

Seizures. Kratom-induced seizures are documented in case reports, including in users without other identified precipitants ^{32Reference 32Afzal H et al. · 2020Case reportA Case of Kratom-induced Seizures — case reportView study →}. Numbers are small and confounding is common, but the signal recurs across reviews of acute adverse effects ^{36,54Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →Reference 54Begum T et al. · 2024ReviewMitragyna speciosa Korth toxicity: Experimental findings and future prospects — reviewView study →}.

Scale of exposure. The 2019 National Survey on Drug Use and Health estimated 0.7% past-year kratom use among US residents aged 12 and over, rising to 10.4% among people with a past-year proxy diagnosis of prescription opioid use disorder — so exposure is concentrated in exactly the population most vulnerable to opioid harm, and is heavily co-occurring with other drug use ^{23Reference 23Palamar JJ · 2021ObservationalPast-Year Kratom Use in the U.S.: Estimates From a Nationally Representative Sample — observationalView study →}.

Poison-centre and surveillance data. US poison centres logged 1,807 kratom exposures between 2011 and 2017, with 65% occurring in 2016–2017 alone; 31.8% resulted in healthcare-facility admission and 51.9% in a serious medical outcome ^{24Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →}. Critically, multiple-substance exposures roughly tripled the odds of both admission (OR 2.80) and a serious outcome (OR 2.25) versus kratom-only exposures ^{24Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →}. Agitation/irritability (22.9%) and tachycardia (21.4%) were the commonest effects; there were 11 deaths, two of them after kratom-only exposure, and seven neonatal exposures of which five involved withdrawal ^{24Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →}. Post-legalisation Thai poison-centre data show a 2.5-fold increase in kratom-related calls and a significant rise in hospital admissions, with ~60% of cases involving co-ingestion ^{39Reference 39Tansuwannarat P et al. · 2026ObservationalFrequency of kratom-related poison center calls before and after kratom legalization in Thailand: current trends — observational surveillanceView study →}.

Mortality — and the confounding. The CDC identified kratom detection in unintentional overdose deaths across 27 states in 2016–2017 ^{25Reference 25Olsen EO et al. · 2019Notes from the Field: Unintentional Drug Overdose Deaths with Kratom Detected — 27 States, July 2016–December 2017View study →}. The interpretive problem is that mitragynine detection is not causation. A Florida case-control study separated 38 deaths where mitragynine was certified as a cause from 111 where it was merely detected: every one of the 111 “associated” deaths involved co-exposures — fentanyl (n=84), cocaine (n=49), ethanol (n=29) — whereas the 38 “induced” deaths had no toxic levels of any other substance and showed higher rates of pulmonary oedema, hepatomegaly and cardiomegaly ^{35Reference 35Iuteri CM et al. · 2026ObservationalCase-control study of mitragynine deaths in Florida — case-controlView study →}. Mean blood mitragynine was 2,486 µg/L in induced fatalities versus 179 µg/L in associated deaths, a concentration-dependent pattern ^{35Reference 35Iuteri CM et al. · 2026ObservationalCase-control study of mitragynine deaths in Florida — case-controlView study →}. Two independently reported single-drug fatal intoxications had postmortem blood concentrations of 2,325 and 3,809 ng/mL ^{33Reference 33Behonick GS et al. · 2022Case reportTwo Single-Drug Fatal Intoxications by Mitragynine — case reportView study →}. A systematic evaluation of 95 published case reports found confounding substances in 32 of 35 deceased cases and 7 of 20 living cases, alongside a pattern of weak toxicology and incomplete medical history, and concluded the case literature is insufficient to establish that kratom alone causes severe acute harm ^{36Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →}.

The defensible reading. Most kratom-detected deaths are polysubstance deaths in which mitragynine is a bystander or a contributor, not the agent. But the case-control and single-drug data establish that fatal mitragynine-only intoxication does occur, apparently at blood concentrations an order of magnitude above those seen in living users ^{33,35,36Reference 33Behonick GS et al. · 2022Case reportTwo Single-Drug Fatal Intoxications by Mitragynine — case reportView study →Reference 35Iuteri CM et al. · 2026ObservationalCase-control study of mitragynine deaths in Florida — case-controlView study →Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →}. Both halves of that sentence are load-bearing. Note also that the sharpest interpretive claims in either direction come from commercially engaged authors (see above) ^{36,37Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →Reference 37Henningfield JE et al. · 2024ReviewKratom safety and toxicology in the public health context: research needs to better inform regulation — review (author conflicts of interest declared)View study →}.

Reproductive and neonatal reports. Neonatal abstinence syndrome following maternal kratom use is reported in the clinical literature, requiring opioid-directed management in the newborn ^{58Reference 58Eldridge WB et al. · 2018Case reportNeonatal Abstinence Syndrome Due to Maternal Kratom Use — case reportView study →}, and poison-centre data recorded neonatal withdrawal among reported exposures ^{24Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →}. Mitragynine is an opioid-active alkaloid with a long terminal half-life and extensive tissue distribution ^{9Reference 9Trakulsrichai S et al. · 2015Pharmacokinetics of mitragynine in manView study →}, so placental transfer and passage into milk should be assumed rather than excluded. There is no controlled human reproductive-safety data. The intake decision belongs on the kratom monograph, not on a molecule page.

Product quality as a toxicological variable. Analysis of commercially available US kratom products by UPLC-MS/MS found substantial variability in alkaloid composition across tablets, films and liquid shots, with frequent mismatches between labelled and actual contents — unreported alkaloids present, listed ones absent, and pharmacologically or toxicologically active species including 7-hydroxymitragynine and 3-dehydromitragynine turning up unannounced ^{40Reference 40Gour A et al. · 2026Mislabeling and Status of Semisynthetic Kratom-Derived Products in the US Market — analyticalView study →}. The semi-synthetic mu-agonist MGM-15 has separately entered the market ^{41Reference 41Gour A et al. · 2025ReviewFrom Kratom to Semi-Synthetic Opioids: The Rise and Risks of MGM-15 — analytical reviewView study →}. Much of what is attributed to “kratom” in harm data is therefore attributable to an uncontrolled, unstandardised product category rather than to the leaf or to mitragynine as such ^{52Reference 52Vadiei N et al. · 2025ReviewThe Impact of Diverse Kratom Products on Use Patterns, Dependence, and Toxicity — reviewView study →}.

Analytical & Forensic Detection

Mitragynine is not detected by standard opiate immunoassays — it is structurally unrelated to the morphinans those assays target — so it is missed on routine drug screens unless specifically sought. Confirmation is by liquid chromatography–tandem mass spectrometry, which is the method used in the human pharmacokinetic study, in the postmortem distribution work, and in commercial product analysis ^{9,34,40Reference 9Trakulsrichai S et al. · 2015Pharmacokinetics of mitragynine in manView study →Reference 34Osawa KA · 2025Postmortem distribution of mitragynine and 7-hydroxymitragynine in 51 cases — forensic analyticalView study →Reference 40Gour A et al. · 2026Mislabeling and Status of Semisynthetic Kratom-Derived Products in the US Market — analyticalView study →}.

For medical-examiner casework, several parameters are established. Mitragynine shows modest postmortem redistribution (mean heart:femoral blood ratio 1.37; 1.08 for 7-hydroxymitragynine), so specimen source matters but does not dominate ^{34Reference 34Osawa KA · 2025Postmortem distribution of mitragynine and 7-hydroxymitragynine in 51 cases — forensic analyticalView study →}. Blood mitragynine:7-hydroxymitragynine ratios are large — roughly 31:1 femoral, 32:1 heart, but only ~15:1 in vitreous humour and ~17:1 in urine — a compartment difference relevant to interpreting a single specimen ^{34Reference 34Osawa KA · 2025Postmortem distribution of mitragynine and 7-hydroxymitragynine in 51 cases — forensic analyticalView study →}. Stability is a practical constraint: refrigerated at 4 °C, mitragynine is stable to 30 days but 7-hydroxymitragynine only to 7 days, and after 60 days the metabolite has lost over half its concentration; methanolic preparations at −20 °C are stable for at least three months ^{34Reference 34Osawa KA · 2025Postmortem distribution of mitragynine and 7-hydroxymitragynine in 51 cases — forensic analyticalView study →}.

Reported concentration ranges give a rough orientation: living users in the case-report literature spanned 5–340 ng/mL, decedents 3.5–7,500 ng/mL ^{36Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →}; single-drug fatalities have been reported at 2,325 and 3,809 ng/mL ^{33Reference 33Behonick GS et al. · 2022Case reportTwo Single-Drug Fatal Intoxications by Mitragynine — case reportView study →}; and medicolegal series continue to accumulate reference distributions ^{35,53Reference 35Iuteri CM et al. · 2026ObservationalCase-control study of mitragynine deaths in Florida — case-controlView study →Reference 53Kliewer RS et al. · 2026Determination of mitragynine concentrations in medicolegal death investigations at the Oklahoma Office of the Chief Medical Examiner — forensic analyticalView study →}. These ranges overlap, which is precisely why a mitragynine result alone does not certify a cause of death.

Its Role in the Plant

Mitragynine is a monoterpene indole alkaloid, built by the pathway that also produces the Rauvolfia, Catharanthus and Uncaria alkaloids: tryptamine (from tryptophan) condenses with the iridoid secologanin to give strictosidine, the universal precursor, which is elaborated through the corynanthe branch to the Mitragyna skeleton ^{45Reference 45Garza-Garcia JJO et al. · 2024ReviewChemical, pharmacological properties and biosynthesis of opioid mitragynine in Mitragyna speciosa (kratom) — reviewView study →}. The pathway is tryptamine-limited in M. speciosa — precursor availability, not downstream enzyme capacity, caps mitragynine accumulation in the plant, which is why elicitors that raise flux into tryptamine also raise mitragynine yield in shoot culture ^{45Reference 45Garza-Garcia JJO et al. · 2024ReviewChemical, pharmacological properties and biosynthesis of opioid mitragynine in Mitragyna speciosa (kratom) — reviewView study →}.

Enzyme identification has advanced quickly. Pathway steps have been reconstructed by expressing candidate M. speciosa enzymes in yeast, and de novo production of kratom monoterpene indole alkaloids in engineered yeast has been achieved ^{46Reference 46Holtz M et al. · 2024Metabolic engineering of yeast for de novo production of kratom monoterpene indole alkaloidsView study →}. Comparative work across Thai M. speciosa accessions shows the alkaloid profile is genotype-associated, not merely environmental — different plants make characteristically different alkaloid mixes ^{44Reference 44Ransden KE et al. · 2026Comparative analysis of monoterpene indole alkaloid composition and genotypic variation in Thai Mitragyna speciosa — analyticalView study →}.

Functionally, the alkaloids are best understood as chemical defence: nitrogenous, bitter, receptor-active secondary metabolites concentrated in the leaf, the tissue most exposed to herbivory. The specific ecological pressures selecting for the corynanthe series in Mitragyna have not been characterised.

Prevalence in Nature

Mitragynine is, for practical purposes, confined to Mitragyna speciosa. It is not a widely distributed plant metabolite; it is a genus- (arguably species-) specific marker, which is why its detection in a biological sample is treated as evidence of kratom exposure ^{34Reference 34Osawa KA · 2025Postmortem distribution of mitragynine and 7-hydroxymitragynine in 51 cases — forensic analyticalView study →}.

Within the leaf it is the dominant alkaloid, accounting for roughly two-thirds of the total alkaloid fraction in Thai material and between about 0.7% and 4.9% of dry leaf weight — a nearly seven-fold range ^{42Reference 42Sengnon N et al. · 2023Seasonal and Geographic Variation in Alkaloid Content of Kratom (Mitragyna speciosa (Korth.) Havil.) from Thailand — analyticalView study →}. That range is not noise. Content varies systematically with season, geographic provenance, altitude and harvest timing, and additionally with genotype: comparative analysis of Thai accessions found genotype-linked differences in the whole monoterpene indole alkaloid profile, not just in mitragynine ^{42,44Reference 42Sengnon N et al. · 2023Seasonal and Geographic Variation in Alkaloid Content of Kratom (Mitragyna speciosa (Korth.) Havil.) from Thailand — analyticalView study →Reference 44Ransden KE et al. · 2026Comparative analysis of monoterpene indole alkaloid composition and genotypic variation in Thai Mitragyna speciosa — analyticalView study →}. Phytochemical characterisation of US-grown material confirms the same alkaloid cast in cultivated plants outside the native range ^{43Reference 43León F et al. · 2009Phytochemical characterization of the leaves of Mitragyna speciosa grown in U.S.A. — analyticalView study →}.

The remaining alkaloid fraction is dominated by close relatives: paynantheine (~8% of alkaloids) and speciogynine (~7%), with 7-hydroxymitragynine typically under 2% of alkaloids and around 0.02–0.04% of leaf despite its outsized pharmacological weight ^{42,43Reference 42Sengnon N et al. · 2023Seasonal and Geographic Variation in Alkaloid Content of Kratom (Mitragyna speciosa (Korth.) Havil.) from Thailand — analyticalView study →Reference 43León F et al. · 2009Phytochemical characterization of the leaves of Mitragyna speciosa grown in U.S.A. — analyticalView study →}. Speciociliatine — a mitragynine diastereomer — and corynantheidine are consistent minor components with their own metabolism and CYP-inhibition profiles ^{7,51Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →Reference 51Kamble SH et al. · 2022Metabolism of Speciociliatine, an Overlooked Kratom Alkaloid for its Potential Pharmacological EffectsView study →}. Oxindoles including mitraphylline, isomitraphylline, rhynchophylline and isorhynchophylline occur as trace constituents, though most published pharmacology for those molecules comes from Uncaria, not from kratom, and should not be transferred ^{10,43Reference 10Manda VK et al. · 2014In vitroEvaluation of in vitro absorption, distribution, metabolism, and excretion (ADME) properties of mitragynine, 7-hydroxymitragynine, and mitraphyllineView study →Reference 43León F et al. · 2009Phytochemical characterization of the leaves of Mitragyna speciosa grown in U.S.A. — analyticalView study →}.

Discovery & Synthesis

Mitragynine was isolated from Mitragyna speciosa leaf and named by Field in 1921, in the same period that yielded mitraversine from a related Mitragyna species. Its full structure — the corynanthe skeleton bearing a 9-methoxy group, making it formally 9-methoxycorynantheidine — was not settled until X-ray crystallographic work in the mid-1960s. The chemistry and pharmacology of the series, including the structural assignments and the analgesic-alkaloid programme that followed, are reviewed comprehensively by Takayama, whose group carried out much of the modern synthetic work ^{15Reference 15Takayama H · 2004ReviewChemistry and pharmacology of analgesic indole alkaloids from the rubiaceous plant, Mitragyna speciosa — reviewView study →}.

Total synthesis. Takayama and co-workers reported synthetic routes to mitragynine and its relatives from the 1990s. The most consequential modern synthesis is the enantioselective total synthesis of both (−)-mitragynine and its unnatural enantiomer (+)-mitragynine reported by Kruegel and colleagues, built on a proline-catalysed Mannich–Michael sequence ^{1Reference 1Kruegel AC et al. · 2016Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor ModulatorsView study →}. It matters pharmacologically as well as chemically: (+)-mitragynine proved much weaker at opioid receptors, establishing that the activity is stereospecific, and the synthetic intermediates enabled the structure–activity work behind the atypical-binding-pose hypothesis ^{1Reference 1Kruegel AC et al. · 2016Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor ModulatorsView study →}. No synthetic route or procedure is described here.

Production today is entirely by extraction from kratom leaf; no synthetic route is commercially competitive with a plant that makes the molecule at several percent of dry weight. The relevant frontier is biological rather than chemical: de novo production of kratom monoterpene indole alkaloids in engineered yeast has been demonstrated, which would in principle allow controlled, standardised supply of individual alkaloids for research ^{46Reference 46Holtz M et al. · 2024Metabolic engineering of yeast for de novo production of kratom monoterpene indole alkaloidsView study →}.

Patents: not yet researched.

Legal Status

Mitragynine’s legal status is genuinely in flux and varies by jurisdiction. What follows is the position as of mid-2026 and should be checked against current notices before being relied on.

United States — federal. Kratom, mitragynine and 7-hydroxymitragynine are not federally scheduled controlled substances. The DEA published a notice of intent to place mitragynine and 7-hydroxymitragynine in Schedule I in August 2016, then withdrew it in October 2016 after unusually large public comment and congressional pushback — an episode analysed in the policy literature as a case of selective use of the available data by both sides ^{38Reference 38Griffin OH · 2018The Scheduling of Kratom and Selective Use of Data — policy analysisView study →}. The FDA has not approved kratom for any use, treats kratom-containing products as unapproved and adulterated, has issued import alerts and warning letters, and advises against consumption. Federal attention has since shifted toward concentrated and semi-synthetic 7-hydroxymitragynine products, which are pharmacologically distinct from leaf kratom and have been the subject of active regulatory movement; the status of those specific products is the part most likely to have changed ^{40,41Reference 40Gour A et al. · 2026Mislabeling and Status of Semisynthetic Kratom-Derived Products in the US Market — analyticalView study →Reference 41Gour A et al. · 2025ReviewFrom Kratom to Semi-Synthetic Opioids: The Rise and Risks of MGM-15 — analytical reviewView study →}. Regulatory-science reviews continue to call for federal oversight of product standards rather than prohibition ^{37Reference 37Henningfield JE et al. · 2024ReviewKratom safety and toxicology in the public health context: research needs to better inform regulation — review (author conflicts of interest declared)View study →}.

United States — state and local. Status is patchwork. A small number of states (commonly including Alabama, Arkansas, Indiana, Rhode Island, Vermont and Wisconsin) prohibit kratom or its alkaloids outright, while a larger and growing number have enacted Kratom Consumer Protection Acts setting labelling, purity, adulteration and minimum-age requirements. Some counties and municipalities ban locally within otherwise-permissive states. Research has examined whether these differing state policy environments track differences in actual use ^{59Reference 59Ellis MS et al. · 2024ObservationalAssociations Between Kratom-Related State Policy Environments and Kratom Use in a Nationally Representative Population — observationalView study →}, and the policy-gap literature identifies the inconsistency itself as a public-health problem ^{37Reference 37Henningfield JE et al. · 2024ReviewKratom safety and toxicology in the public health context: research needs to better inform regulation — review (author conflicts of interest declared)View study →}.

Thailand. Kratom was banned in 1943 and remained illegal for nearly eight decades. It was removed from Thailand’s narcotics list on 24 August 2021, effectively legalising use, and is now a significant agricultural crop. Post-legalisation surveillance found kratom-related poison-centre calls increased 2.5-fold, with a significant rise in hospital admissions, though the clinical presentation profile was unchanged ^{39Reference 39Tansuwannarat P et al. · 2026ObservationalFrequency of kratom-related poison center calls before and after kratom legalization in Thailand: current trends — observational surveillanceView study →}.

Elsewhere. Malaysia controls kratom under poisons legislation. Australia, and a number of European and Asian countries, prohibit kratom or mitragynine outright. Neither kratom nor mitragynine is scheduled under the 1961 or 1971 UN drug conventions, so international control is entirely a matter of national law — which is the main reason the map is so uneven.

Toxicity & Safety

Mitragynine carries a toxic flag here. The justification is the combination of a documented dependence and withdrawal syndrome in long-term users, a prospectively identified hepatotoxicity signal, seizure reports, and confirmed single-substance fatal intoxications — set against the genuine mitigating facts that its respiratory depression has a metabolic ceiling and that the large majority of kratom-detected deaths are polysubstance ^{4,26,30,32,33,35,36Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →Reference 26Singh D et al. · 2014ObservationalKratom (Mitragyna speciosa) dependence, withdrawal symptoms and craving in regular users — observational cohortView study →Reference 30Ahmad J et al. · 2021ObservationalLiver injury associated with kratom, a popular opioid-like product: Experience from the U.S. drug induced liver injury network — observational cohortView study →Reference 32Afzal H et al. · 2020Case reportA Case of Kratom-induced Seizures — case reportView study →Reference 33Behonick GS et al. · 2022Case reportTwo Single-Drug Fatal Intoxications by Mitragynine — case reportView study →Reference 35Iuteri CM et al. · 2026ObservationalCase-control study of mitragynine deaths in Florida — case-controlView study →Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →}.

Dependence, Withdrawal & Use Disorder

Tolerance, physical dependence, craving and an opioid-like withdrawal syndrome are documented in cohorts of regular long-term users ^{26,27Reference 26Singh D et al. · 2014ObservationalKratom (Mitragyna speciosa) dependence, withdrawal symptoms and craving in regular users — observational cohortView study →Reference 27Singh D et al. · 2018ObservationalSeverity of Kratom (Mitragyna speciosa Korth.) Psychological Withdrawal Symptoms — observationalView study →}. Kratom use disorder is described in the clinical literature as a real presentation with contested criteria and no agreed treatment pathway ^{29Reference 29Smith KE et al. · 2024ReviewControversies in Assessment, Diagnosis, and Treatment of Kratom Use Disorder — reviewView study →}. Dependence risk appears to scale sharply with product concentration — extracts and 7-hydroxymitragynine-enriched products are not equivalent to traditional leaf ^{52Reference 52Vadiei N et al. · 2025ReviewThe Impact of Diverse Kratom Products on Use Patterns, Dependence, and Toxicity — reviewView study →}.

Hepatotoxicity

The US Drug-Induced Liver Injury Network prospectively captured kratom-associated liver injury, typically cholestatic or mixed, presenting within weeks of initiation ^{30Reference 30Ahmad J et al. · 2021ObservationalLiver injury associated with kratom, a popular opioid-like product: Experience from the U.S. drug induced liver injury network — observational cohortView study →}; case reports describe the same pattern with recovery on cessation and conservative management ^{31Reference 31Fernandes CT et al. · 2019Case reportKratom-Induced Cholestatic Liver Injury and Its Conservative Management — case reportView study →}. Incidence and mechanism are both unknown.

Neurological & Cardiovascular Effects

Seizures are reported in case reports of kratom users ^{32Reference 32Afzal H et al. · 2020Case reportA Case of Kratom-induced Seizures — case reportView study →}, and reviews of acute adverse effects describe pulmonary, cardiovascular, hepatic, renal, gastrointestinal and neurological presentations across the case literature — heavily confounded by co-exposures ^{36,54Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →Reference 54Begum T et al. · 2024ReviewMitragyna speciosa Korth toxicity: Experimental findings and future prospects — reviewView study →}. Poison-centre data identify agitation/irritability and tachycardia as the commonest single-substance effects ^{24Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →}, and Thai surveillance found tachycardia and palpitations the most frequent findings ^{39Reference 39Tansuwannarat P et al. · 2026ObservationalFrequency of kratom-related poison center calls before and after kratom legalization in Thailand: current trends — observational surveillanceView study →}.

Drug Interactions

Mitragynine is a potent competitive CYP2D6 inhibitor in vitro (Ki ~1.1 µM) and a time-dependent CYP3A inhibitor shown clinically to inhibit intestinal CYP3A ^{7,8Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}. Co-consumption with drugs cleared substantially by CYP3A may precipitate serious interactions ^{8Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}. CYP2D6-substrate interactions are predicted but were not observed at a single low tea dose, which does not exclude them at habitual exposure ^{7,8Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →}. Additive sedation and respiratory depression with other opioids, benzodiazepines and alcohol is the pharmacologically obvious risk, and polysubstance exposure is the single strongest predictor of serious outcome in the surveillance data ^{24Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →}.

Reproductive & Neonatal

Neonatal abstinence syndrome after maternal kratom use is documented ^{58Reference 58Eldridge WB et al. · 2018Case reportNeonatal Abstinence Syndrome Due to Maternal Kratom Use — case reportView study →}, and neonatal withdrawal appears in poison-centre records ^{24Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →}. There is no controlled human reproductive-safety data for kratom or for mitragynine.

Product Integrity

Commercial products show substantial alkaloid variability and frequent labelling inaccuracy, sometimes containing unreported 7-hydroxymitragynine, 3-dehydromitragynine or the semi-synthetic MGM-15 ^{40,41Reference 40Gour A et al. · 2026Mislabeling and Status of Semisynthetic Kratom-Derived Products in the US Market — analyticalView study →Reference 41Gour A et al. · 2025ReviewFrom Kratom to Semi-Synthetic Opioids: The Rise and Risks of MGM-15 — analytical reviewView study →}. For an unscheduled but unstandardised product category, this is a first-order safety problem rather than a footnote.

Safety at a Glance

☠️ ToxicDependence riskLiver riskDrug interactionsControlled substanceSedating

• The molecular pharmacology is unusually well characterised for a plant alkaloid — receptor function, metabolic activation route, CYP interaction constants and forensic distribution are all defined in the isolate ^{1,3,7,34Reference 1Kruegel AC et al. · 2016Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor ModulatorsView study →Reference 3Kruegel AC et al. · 2019Kruegel AC, et al. (2019). 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects. ACS Central Science. https://pubmed.ncbi.nlm.nih.gov/31263758/View study →Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →Reference 34Osawa KA · 2025Postmortem distribution of mitragynine and 7-hydroxymitragynine in 51 cases — forensic analyticalView study →}.
• Genuine dependence and withdrawal. Tolerance, craving and an opioid-like withdrawal syndrome are documented in long-term users; kratom use disorder is a recognised, if contested, clinical presentation ^{26,27,29Reference 26Singh D et al. · 2014ObservationalKratom (Mitragyna speciosa) dependence, withdrawal symptoms and craving in regular users — observational cohortView study →Reference 27Singh D et al. · 2018ObservationalSeverity of Kratom (Mitragyna speciosa Korth.) Psychological Withdrawal Symptoms — observationalView study →Reference 29Smith KE et al. · 2024ReviewControversies in Assessment, Diagnosis, and Treatment of Kratom Use Disorder — reviewView study →}.
• Hepatotoxicity signal. Prospectively identified cholestatic/mixed liver injury within weeks of starting use; incidence and mechanism unknown ^{30,31Reference 30Ahmad J et al. · 2021ObservationalLiver injury associated with kratom, a popular opioid-like product: Experience from the U.S. drug induced liver injury network — observational cohortView study →Reference 31Fernandes CT et al. · 2019Case reportKratom-Induced Cholestatic Liver Injury and Its Conservative Management — case reportView study →}.
• Fatal single-substance intoxications are documented at blood concentrations roughly an order of magnitude above those in living users — even though most kratom-detected deaths are polysubstance ^{33,35,36Reference 33Behonick GS et al. · 2022Case reportTwo Single-Drug Fatal Intoxications by Mitragynine — case reportView study →Reference 35Iuteri CM et al. · 2026ObservationalCase-control study of mitragynine deaths in Florida — case-controlView study →Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →}.
• Real drug-interaction surface. Potent in-vitro CYP2D6 inhibition and clinically demonstrated intestinal CYP3A inhibition; co-use with CYP3A-cleared drugs, opioids, benzodiazepines or alcohol is the main hazard ^{7,8,24Reference 7Kamble SH et al. · 2020Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloidsView study →Reference 8Tanna RS et al. · 2023RCTClinical Assessment of the Drug Interaction Potential of the Psychotropic Natural Product Kratom — randomised clinical pharmacokinetic studyView study →Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →}.
• The “safer opioid” argument is not settled. G-protein bias is real in the assay, but the β-arrestin hypothesis it rests on has weakened, and the respiratory ceiling is better explained by metabolic saturation than by bias ^{4,47,48,49Reference 4Hill R et al. · 2022AnimalThe respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine — mouse in vivoView study →Reference 47Gillis A et al. · 2020Low intrinsic efficacy for G protein activation can explain the improved side effect profiles of new opioid agonistsView study →Reference 48Stahl EL · 2022Low Intrinsic Efficacy Alone Cannot Explain the Improved Side Effect Profiles of New Opioid AgonistsView study →Reference 49Kliewer A et al. · 2020AnimalMorphine-induced respiratory depression is independent of β-arrestin2 signalling — mouse genetic modelView study →}.
• Seizures reported in case reports, with small numbers and frequent confounding ^{32,36Reference 32Afzal H et al. · 2020Case reportA Case of Kratom-induced Seizures — case reportView study →Reference 36Smallets S et al. · 2025Systematic reviewThe acute adverse health effects of kratom: an evaluation of case reports — systematic review of case reports (author conflicts of interest declared)View study →}.
• Product content is unreliable. Frequent mislabelling, variable alkaloid load, and undisclosed 7-hydroxymitragynine or semi-synthetic agonists in some commercial products ^{40,41Reference 40Gour A et al. · 2026Mislabeling and Status of Semisynthetic Kratom-Derived Products in the US Market — analyticalView study →Reference 41Gour A et al. · 2025ReviewFrom Kratom to Semi-Synthetic Opioids: The Rise and Risks of MGM-15 — analytical reviewView study →}.
• Neonatal withdrawal reported after maternal use; no controlled reproductive-safety data exists ^{24,58Reference 24Post S et al. · 2019ObservationalKratom exposures reported to United States poison control centers: 2011-2017 — observational surveillanceView study →Reference 58Eldridge WB et al. · 2018Case reportNeonatal Abstinence Syndrome Due to Maternal Kratom Use — case reportView study →}.

Dosage

No dose for effect is given here, and none should be inferred from the figures below. Mitragynine is not an approved medicine anywhere, has never been administered to humans as an isolate in a published controlled trial, and is legally restricted in many jurisdictions. What follows are research and forensic reference parameters, recorded so the pharmacology above can be read in context.

Two caveats make any leaf figure a poor proxy for alkaloid exposure. Leaf mitragynine content spans roughly 0.7–4.9% of dry weight across genotype, season and provenance ^{42,44Reference 42Sengnon N et al. · 2023Seasonal and Geographic Variation in Alkaloid Content of Kratom (Mitragyna speciosa (Korth.) Havil.) from Thailand — analyticalView study →Reference 44Ransden KE et al. · 2026Comparative analysis of monoterpene indole alkaloid composition and genotypic variation in Thai Mitragyna speciosa — analyticalView study →}, and commercial products are frequently mislabelled, sometimes containing undisclosed 7-hydroxymitragynine or semi-synthetic agonists ^{40,41Reference 40Gour A et al. · 2026Mislabeling and Status of Semisynthetic Kratom-Derived Products in the US Market — analyticalView study →Reference 41Gour A et al. · 2025ReviewFrom Kratom to Semi-Synthetic Opioids: The Rise and Risks of MGM-15 — analytical reviewView study →}.

These are research and forensic reference figures, not a personal recommendation.

References

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