55 papers on kratom, its alkaloids, and what happens to people when a drug they depend on is taken away. All but one are peer-reviewed, and all of them are free to read. We summarise what each found, say what we think it is good for, and link the original so you can check us.
Some of these papers damage our position. They are marked Cuts against us and summarised straight, because we ask legislators to read the bill instead of somebody's summary of it and we do not get an exemption from that.
The case this supports is not that kratom or its alkaloids are harmless — the literature will not carry that, and an argument built on it falls over the first time somebody opens PubMed. The case is that prohibition is the wrong instrument, that the evidence for the specific lines being drawn does not exist, and that cutting people off has a cost the people drawing those lines have not counted.
We do not rehost any of these papers. For every one, what you get is a summary in our own words, at most a sentence quoted with attribution, and a link to the original. That is lawful for all fifty-five regardless of licence, which is the point of doing it that way.
The licence is printed on every card so you can check us rather than trust us. Thirteen carry NoDerivatives terms, which permit quoting but not republishing a reformatted copy. Two are marked All rights reserved — free to read on PubMed Central, but carrying no reuse grant at all. One of those looks open at a glance and is not: its only permission came from PubMed Central’s COVID-era access scheme, which expired with the WHO pandemic declaration in May 2023. Free to read is not a licence, and we checked each of those against the publisher’s own record rather than against a summary of it.
Where a published version sits behind a paywall we link the free preprint and label it. If you hold rights in anything here and think we have got a licence wrong, write to info@havenaccess.org and we will fix it.
Human data - pharmacokinetics, phase 1 safety, abuse potential, and what users actually report. Thin compared with the animal literature, which is itself part of the argument.
Phase 1 study of single doses of mitragynine in humans, looking at safety and neurocognitive function.
Why it matters: An actual controlled human trial of the primary leaf alkaloid. Cite it when someone asserts nothing about kratom has ever been studied properly in people.
Read the paper (opens in a new tab) doi:10.1007/s00213-024-06734-2
Assessed abuse-potential-related effects of oral dried kratom leaf powder in healthy participants, single and multiple doses.
Why it matters: Abuse potential is a scheduling factor. A dedicated human study of leaf powder is directly responsive to the statutory criteria, rather than to a headline.
Read the paper (opens in a new tab) doi:10.1002/dta.70089
Bayesian integrated pharmacokinetic model treating mitragynine and its active metabolite 7-OH as one coupled system.
Why it matters: Modelling work that matters for thresholds: it describes how the two move together, which is the thing a single static percentage cap cannot represent.
Read the paper (opens in a new tab) doi:10.5599/admet.3170
Clinical pharmacokinetic assessment of kratom in healthy adults, framed explicitly around how little rigorous human PK existed despite serious safety claims being made.
Why it matters: Useful for the meta-argument: regulators have been drawing numeric lines for years on a human evidence base the researchers themselves describe as lacking.
Read the paper (opens in a new tab) doi:10.3390/pharmaceutics14030620
JAMA Network Open ecological momentary assessment: US adults recorded kratom use, effects and motivations in real time rather than by recall.
Why it matters: The strongest available picture of who actually uses kratom and why - pain, mood, and self-managing substance use disorders. Counters the assumption that use is recreational by default.
Read the paper (opens in a new tab) doi:10.1001/jamanetworkopen.2023.53401
Measured mitragynine and 7-OH in blood after single and repeated daily doses of dried kratom leaf powder in humans.
Why it matters: One of very few human pharmacokinetic datasets that exists. Any claim about what concentration a person actually reaches from leaf has to start here rather than from an animal dose.
Read the paper (opens in a new tab) doi:10.3390/molecules29050984
Scientific expert forum convened to reach conclusions on kratom dependence and withdrawal.
Why it matters: A consensus document rather than a single study. Useful where you need the field's centre of gravity on withdrawal rather than the most alarming individual case.
Read the paper (opens in a new tab) doi:10.1016/j.dadr.2023.100142
Human plasma pharmacokinetics of mitragynine and 7-OH after single and multiple doses of a kratom extract.
Why it matters: Extract, not leaf - so it speaks to the middle ground between traditional preparations and isolated 7-OH, which is exactly the range most state caps are written about.
Read the paper (opens in a new tab) doi:10.1093/jat/bkag042
The receptor pharmacology. This is the load-bearing distinction on the whole site: the plant and the isolate are not the same drug, and the papers say why.
The 2019 ACS Central Science paper establishing 7-OH as an active metabolite of mitragynine and a key mediator of its analgesic effect.
Why it matters: Foundational, and it cuts both ways honestly. It is the citation for 7-OH being produced in the body from ordinary leaf - which complicates any rule written as though 7-OH only ever arrives from a lab.
Read the paper (opens in a new tab) doi:10.1021/acscentsci.9b00141
Translational Psychiatry review of molecular mechanisms and epigenetic factors in kratom use and dependence.
Why it matters: Takes dependence seriously without treating it as equivalent to classical opioid addiction. That is the honest register for talking about dependence at all.
Read the paper (opens in a new tab) doi:10.1038/s41398-026-04022-5
British Journal of Pharmacology study of kratom alkaloids and synthetic analogues as potential treatments for alcohol use disorder.
Why it matters: Evidence of therapeutic potential beyond pain, which speaks to the 'currently accepted medical use' limb of scheduling.
Published under the G-protein-bias framing that has since been qualified. The therapeutic finding stands; the mechanism labelling in the title has not aged well.
Read the paper (opens in a new tab) doi:10.1111/bph.14913
In silico investigation of how mitragynine and 7-OH are metabolised.
Why it matters: Background for the metabolite argument. Modest on its own; useful as corroboration alongside the human PK work.
Read the paper (opens in a new tab) doi:10.1186/s13104-019-4461-3
Review of indole alkaloids as biased opioid receptor modulators and their potential for reduced adverse effects.
Why it matters: Sets out the therapeutic thesis. Read it alongside the mechanism papers that qualify the bias claim rather than on its own.
Frames its case around biased agonism. That framing has been substantially walked back by the group that originated it - see the arrestin and phosphorylation-deficient receptor papers under mechanism.
Read the paper (opens in a new tab) doi:10.3390/ph19030397
Review of how kratom alkaloids interact with metabolic enzymes, receptors and cellular barriers.
Why it matters: Where drug-interaction questions get answered. Relevant to labeling and warning requirements, which we support, as against prohibition, which we do not.
Read the paper (opens in a new tab) doi:10.3389/fphar.2021.751656
Molecular dynamics and Markov state modelling mapping why mitragynine is a partial agonist at the mu-opioid receptor with submaximal efficacy.
Why it matters: This is the surviving mechanistic story - low intrinsic efficacy, not 'biased agonism'. Use this framing rather than the bias one, which the originating lab walked back.
Read the paper (opens in a new tab) doi:10.1038/s41598-026-43251-y
Systematic evaluation of binding affinity and functional activity across many kratom alkaloids at human opioid receptors.
Why it matters: Kratom is not one drug. Over fifty alkaloids with different activities is the pharmacological basis for objecting to rules that treat the whole plant as a single substance.
Read the paper (opens in a new tab) doi:10.3389/fphar.2026.1763551
Nature Communications: selective chemical modification of Mitragyna alkaloids identified a structural 'molecular switch' that tunes opioid receptor behaviour.
Why it matters: Concrete evidence that this scaffold is a live medicinal-chemistry programme. Directly relevant to the circularity argument - scheduling forecloses the research that would answer the questions scheduling is justified by.
Read the paper (opens in a new tab) doi:10.1038/s41467-021-23736-2
Respiratory depression is what makes an opioid lethal. This is where the evidence is most direct, most contested, and least comfortable for us.
Rat study finding mitragynine and 7-OH have opposite effects on breathing, and that 7-OH is a substantially more potent respiratory depressant than morphine.
Why it matters: This is the single most important paper here to read before writing anything. It is the primary evidence behind the potency figures used to justify scheduling concentrated 7-OH, and it does not support a claim that isolated 7-OH is benign. Our position survives it - the argument is that Schedule I is the wrong instrument and that the specific threshold is underivable, not that the compound is harmless - but any argument that ignores this paper is one refutation away from collapsing.
Published version is paywalled; this links the free bioRxiv preprint of the same study.
Read the paper (opens in a new tab) doi:10.1016/j.jpet.2025.103720
Compared novel and classical opioids for their potential to induce respiratory depression in mice.
Why it matters: Calibration. It places whatever number is being quoted about a kratom alkaloid next to the same measurement for drugs that are legally prescribed every day.
Read the paper (opens in a new tab) doi:10.1111/bph.16199
JPET commentary describing atypical respiration patterns produced by kratom alkaloids, building on the primary rat work.
Why it matters: The interpretive companion to the bidirectional-breathing study. Read them together - this one supplies the qualification, that one supplies the numbers.
Read the paper (opens in a new tab) doi:10.1016/j.jpet.2026.104326
Compared respiratory effects of oral mitragynine against oxycodone in rats.
Why it matters: A direct head-to-head against a scheduled opioid, which is the comparison scheduling decisions implicitly make. Note the authors' industry-adjacent affiliations and disclose them when citing.
Read the paper (opens in a new tab) doi:10.1007/s00213-022-06244-z
Found that mitragynine's respiratory depressant effects are limited by its conversion to 7-OH - the metabolic step itself constrains the effect.
Why it matters: One of the most useful mechanistic findings for distinguishing leaf from isolate: what happens when 7-OH is produced slowly in the body is not what happens when it is swallowed directly.
Read the paper (opens in a new tab) doi:10.1111/bph.15832
Analytical chemistry on real products. The gap between what a label says and what is in the bottle is large, documented, and not a matter of opinion.
Case report of severe withdrawal from concentrated 7-OH taken in combination with nicotine pouches.
Why it matters: A single case report proves little on its own, and we say so about case reports elsewhere in this library - so we hold ourselves to it here. Cite it as what it is: a documented account of dependence on a concentrated product, which is consistent with our position that these products differ from leaf.
Read the paper (opens in a new tab) doi:10.7759/cureus.98386
An open letter from addiction clinicians calling on colleagues to act on concentrated synthetic 7-OH.
Why it matters: Read this to understand who is actually on which side. Clinicians treating opioid addiction are not a hostile lobby, and treating their concern as bad faith is how advocacy loses credible people.
Read the paper (opens in a new tab) doi:10.2147/SAR.S583572
Review arguing kratom has evolved from a traditional remedy into a public-health threat via concentrated 7-OH products, noting that traditional leaf and tea preparations involve only trace 7-OH exposure.
Why it matters: The most prominent hostile review, and it concedes the premise we care about most: under traditional preparation, 7-OH exposure is minimal. Its own leaf-concentration figures are useful even where its conclusions are not.
Read the paper (opens in a new tab) doi:10.1080/13880209.2025.2590311
Integrated in silico and in vitro genotoxicity assessment of a 7-OH-enriched kratom preparation.
Why it matters: Genotoxicity is a serious endpoint and this is a direct assessment of an enriched preparation. Include it because leaving it out would be exactly the selective reading we accuse regulators of.
Read the paper (opens in a new tab) doi:10.1016/j.toxrep.2026.102206
Developed a multicriteria LC-MS approach to avoid falsely identifying 7-OH in kratom products, where related alkaloids can be mistaken for it.
Why it matters: Directly relevant to enforcement. A cap is only as good as the assay behind it, and this paper shows the assay can get it wrong in the direction that would condemn ordinary leaf.
Read the paper (opens in a new tab) doi:10.1021/jasms.6c00088
Tested products sold as 'kratom extract' and found 7-OH at 22-75 mg/g - 5 to 28% above even their own label claims - with alkaloid profiles inconsistent with kratom leaf and concentrations achievable only synthetically.
There is an urgent need to differentiate kratom, which has been safely consumed for centuries, from 7-hydroxymitragynine, which may pose a significant risk to public health.
Why it matters: The most quotable paper in the corpus for the distinction we draw. The authors' conclusion is our position stated by analytical chemists: these products are not kratom extracts as labelled, and there is an urgent need to differentiate kratom from concentrated 7-OH.
Two of four authors disclose consulting work as regulatory consultants on botanical dietary ingredients including kratom. Say so when you cite it.
Read the paper (opens in a new tab) doi:10.1093/jaoacint/qsaf094
Case reports, poison-centre data and risk assessments - alongside the papers explaining what those instruments can and cannot support.
MMWR report on rising kratom-related calls to US poison centres, 2015-2025, linked to the shift from leaf preparations to high-potency extracts.
Why it matters: The headline number most often quoted at us. Cite it directly rather than around it - and note that CDC's own definitions mean an 'exposure' call records a call, not a finding of toxicity.
Read the paper (opens in a new tab) doi:10.15585/mmwr.mm7511a1
EFSA health risk assessment of botanical preparations of Mitragyna speciosa.
Why it matters: A European regulator's assessment, useful as a non-US comparator when someone asserts an international consensus for prohibition.
Read the paper (opens in a new tab) doi:10.2903/j.efsa.2022.e200415
Mini-review arguing kratom may function as a harm-reduction agent for substance use disorders where conventional treatment is inaccessible or refused.
Why it matters: States the affirmative case directly: many people use kratom instead of something more dangerous, and removing it does not return them to nothing.
Read the paper (opens in a new tab) doi:10.3389/fpubh.2024.1416689
Reviews kratom safety and toxicology specifically in terms of what regulators need and do not yet have.
Why it matters: Written to inform regulation rather than to attack or defend. The best single citation for 'here is what we do not know', which is the honest foundation of our threshold argument.
Read the paper (opens in a new tab) doi:10.3389/fphar.2024.1403140
Systematic evaluation of the case reports on which most claims of kratom-associated harm rest.
Why it matters: The methodological answer to the case-report literature: it examines what those reports can actually establish, including polysubstance involvement and missing product characterisation.
Read the paper (opens in a new tab) doi:10.3389/fphar.2025.1620601
Not about kratom at all. This is the opioid-policy literature on abrupt discontinuation, and it is the best-evidenced argument against prohibition we have.
North Carolina study associating rapid opioid dose reduction with subsequent overdose and opioid use disorder.
Why it matters: A second jurisdiction reaching the same conclusion. Two independent datasets showing the same direction is materially stronger than one.
Read the paper (opens in a new tab) doi:10.1001/jamanetworkopen.2022.9191
JAMA Network Open comparative effectiveness study of opioid tapering or abrupt discontinuation versus no dosage change.
Why it matters: Directly comparative, which is what makes it hard to wave away. Abrupt discontinuation is what a ban does to a dependent user, without the taper.
Read the paper (opens in a new tab) doi:10.1001/jamanetworkopen.2022.26523
MMWR on illicitly manufactured fentanyl overdose deaths with xylazine detected.
Why it matters: This is what the unregulated supply looks like. The relevant comparison for any ban is not kratom against nothing, but kratom against what replaces it.
Read the paper (opens in a new tab) doi:10.15585/mmwr.mm7226a4
On integrating harm reduction into outpatient opioid use disorder treatment, and the limits of requiring abstinence.
Why it matters: The framework we are arguing for, in a clinical setting. Abstinence-only requirements drive people out of care; prohibition is the same design at population scale.
Read the paper (opens in a new tab) doi:10.1007/s11606-021-06904-4
Two nested case-control studies in PAIN finding associations between prescription opioid discontinuation and death by suicide or unintentional overdose.
Why it matters: The cutoff argument with mortality as the endpoint. When a ban removes a supply people depend on, this is the literature describing what follows.
Read the paper (opens in a new tab) doi:10.1097/j.pain.0000000000003824
Examines how racial attitudes, political affiliation and stigma shape public support for opioid policy responses.
Why it matters: Uncomfortable and worth reading. Drug policy is not decided on evidence alone, and knowing what actually moves support is more useful than assuming better data will.
Read the paper (opens in a new tab) doi:10.1016/j.ypmed.2022.107034
CDC authors in Lancet Regional Health estimate overdose deaths fell 25% year-on-year, attributing it largely to fentanyl saturation and a declining population using drugs rather than to enforcement.
Why it matters: Important for honesty about causation. When overdose numbers move, this is the paper explaining what actually drives them - which is a caution against crediting or blaming any single prohibition.
Read the paper (opens in a new tab) doi:10.1016/j.lana.2025.101226
How withdrawal is measured and managed, and how buprenorphine got approved. Context for any claim about dependence.
History of the discovery, development and FDA approval of buprenorphine for opioid use disorder.
Why it matters: The precedent case: a partial mu agonist, once treated with deep suspicion, became a first-line treatment. Directly relevant to what scheduling forecloses.
Read the paper (opens in a new tab) doi:10.1016/j.dadr.2023.100133
Multisite emergency department study measuring how often buprenorphine initiation actually precipitates withdrawal.
Why it matters: Quantifies a risk that is often asserted rather than measured. A model for demanding the same of claims made about kratom.
Read the paper (opens in a new tab) doi:10.1001/jamanetworkopen.2023.6108
Proposes an operational definition of precipitated opioid withdrawal, which previously had none.
Why it matters: A reminder that widely used clinical terms often lack agreed definitions - the same problem as 'kratom product' in most statutes.
Read the paper (opens in a new tab) doi:10.3389/fpsyt.2023.1141980
Review of effective management of opioid withdrawal symptoms as a gateway into treatment.
Why it matters: Establishes that withdrawal is a managed clinical event, not an argument for prohibition.
Read the paper (opens in a new tab) doi:10.1111/ajad.12862
Pharmacology of buprenorphine microinduction, developed to start treatment without triggering precipitated withdrawal.
Why it matters: Shows how much clinical engineering goes into managing a transition between opioids - the kind of care a ban replaces with nothing.
Read the paper (opens in a new tab) doi:10.1007/s40261-021-01032-7
Scoping review of opioid withdrawal assessment scales and technologies.
Why it matters: Background for evaluating any claim that kratom withdrawal is severe or mild. Ask which instrument was used before accepting either.
Read the paper (opens in a new tab) doi:10.1186/s12911-019-0834-8
General receptor pharmacology. Here because arguments about kratom keep turning on claims about bias, tolerance and respiratory depression that were settled elsewhere.
Identifies dual mechanisms by which opioids depress breathing in the inspiratory rhythm-generating network.
Why it matters: The physiological detail behind every respiratory-depression claim. Useful when a paper reports 'reduced minute volume' and you need to know what was measured.
Read the paper (opens in a new tab) doi:10.7554/elife.67523
Evaluated opioid-induced respiratory depression with oliceridine versus morphine, including how endpoints were defined.
Why it matters: A worked example of measuring respiratory safety in humans, and of how much the chosen endpoint determines the answer.
Read the paper (opens in a new tab) doi:10.1007/s40261-020-00936-0
Review of how G-protein-biased mu agonists influence addiction-related behaviours.
Why it matters: Rounds out the bias picture on the dependence side rather than the breathing side.
Read the paper (opens in a new tab) doi:10.1007/s43440-021-00251-1
Review of the molecular mechanisms of opioid tolerance, from receptors through inflammatory mediators.
Why it matters: Background for any claim about escalating use. Tolerance has mechanisms, and they are not interchangeable with addiction.
Read the paper (opens in a new tab) doi:10.3892/etm.2021.10437
Review of how repeated opioid exposure produces dependence and creates vulnerability to addiction.
Why it matters: Keeps dependence and addiction distinct, which most policy writing conflates - including writing that is friendly to us.
Read the paper (opens in a new tab) doi:10.12688/f1000research.8369.1
Genetic and pharmacological work at the mu receptor finding arrestin-3 engagement limits tolerance rather than driving respiratory depression.
Why it matters: Directly contradicts the mechanism the bias argument depends on. Read this before using 'does not recruit beta-arrestin' in any copy.
Read the paper (opens in a new tab) doi:10.1038/s41386-021-01054-x
Phosphorylation-deficient G-protein-biased mu receptors improved analgesia but worsened other side effects.
Why it matters: Further evidence that bias does not straightforwardly mean safety. Cite alongside the PZM21 replication.
Read the paper (opens in a new tab) doi:10.1038/s41467-018-08162-1
Broad review of the neurobiology of addiction and the limits of current prevention and treatment.
Why it matters: General grounding. Useful mainly for its candour about how modest treatment outcomes are, which is the backdrop to anything people are using kratom instead of.
Read the paper (opens in a new tab) doi:10.1111/nyas.13989
Re-examined PZM21, reported as a biased agonist without respiratory depression, and found it does depress respiration and induces tolerance.
Why it matters: The clearest documented case of a biased-agonist safety claim failing replication. This is why we do not build arguments on bias.
Read the paper (opens in a new tab) doi:10.1111/bph.14224
Citations are extracted from the papers themselves rather than retyped, so a DOI on this page is the DOI on the paper. The summaries and the “why it matters” notes are ours, and they are opinion — the papers are not. Where authors disclose funding or consulting that bears on how you should read a result, we say so on the card.
Nothing here is medical or legal advice. Page generated 2026-08-29.
