Research on kratom alkaloids has accelerated substantially since 2016. What was once a niche area of natural products chemistry and Southeast Asian ethnobotany has become a legitimate focus of opioid pharmacology research, attracting funding from the National Institutes of Health, involvement from major academic institutions, and publication in high-impact peer-reviewed journals.
This article provides an educational survey of where the research stands as of 2025, what questions researchers are asking, what findings have emerged, what remains unresolved, and what methodological challenges the field faces. It is descriptive rather than evaluative; the goal is to accurately characterise the science, not to draw conclusions about the compounds' therapeutic value or risk profile.
The Funding Landscape
Federal research investment in kratom science has come primarily from two NIH institutes with distinct but overlapping interests:
National Institute on Drug Abuse (NIDA)
NIDA's investment in kratom research reflects its mission to advance the science of drug abuse and addiction. Funded research areas have included: characterisation of kratom alkaloid pharmacology at opioid receptors; preclinical studies of dependence and self-administration behaviour; epidemiological surveys of kratom use patterns in the general population; and the development of kratom-specific drug testing methodologies. NIDA has framed kratom alkaloid research within the broader context of the opioid crisis, both as a substance with its own abuse potential and as a source of novel chemical scaffolds for analgesic drug discovery.
National Center for Complementary and Integrative Health (NCCIH)
NCCIH's research programme has taken a somewhat different approach, funding research on kratom as a natural product that many Americans are self-administering, often without medical supervision. NCCIH-funded work has included surveys of kratom consumer motivations, online community analysis of self-reported use patterns, and systematic literature reviews. NCCIH's framing acknowledges the need to understand how kratom is actually being used before drawing conclusions about policy.
Key Academic Research Groups
Several academic research groups have produced a substantial proportion of the published kratom alkaloid literature:
- The Majumdar and Faouzi laboratories (Icahn School of Medicine at Mount Sinai): significant work on kratom alkaloid structure-activity relationships and opioid receptor signalling bias
- The McCurdy group (University of Florida): extensive work on kratom alkaloid chemistry, synthesis, and pharmacology over more than a decade
- The Boyer group (University of Massachusetts Medical School): survey-based research on kratom user demographics and self-reported use patterns
- The Henningfield group: pharmacokinetic and clinical translational research
- Multiple groups in Malaysia and Thailand where the plant is native: ethnobotanical documentation and regional use pattern research
Active Research Questions
1. Biased Agonism and the Beta-Arrestin Question
Whether kratom alkaloids, particularly 7-hydroxymitragynine, function as G-protein biased agonists at MOR in clinically relevant ways remains one of the most scientifically contested questions in the field. Preclinical data supporting biased agonism has been published from multiple groups. However, the translation of biased agonism from in vitro assays to animal models to human clinical outcomes has proven far more complicated than early researchers anticipated.
Two developments have complicated the biased agonism story. First, a 2020 paper in Cell challenged the simplistic G-protein bias/beta-arrestin model for respiratory depression, finding that beta-arrestin-2 knockout mice showed no reduction in opioid-induced respiratory depression, suggesting beta-arrestin-2 involvement in respiratory depression is less central than previously believed.
Second, drugs explicitly designed as G-protein biased MOR agonists (oliceridine being the clinical example) have been approved but have not shown the dramatic safety advantages that the early biased agonism hypothesis predicted. The kratom alkaloid research community is actively grappling with these developments.
2. New Synthetic Analogues Based on the 7-OH Scaffold
One of the most active research directions involves using the 7-OH molecular scaffold as a starting point for systematic chemical modification. Research groups have synthesised dozens of analogues with modifications at various positions on the molecular scaffold, testing each for MOR binding affinity, functional efficacy, G-protein vs beta-arrestin bias ratio, and selectivity across opioid receptor subtypes.
This medicinal chemistry work is producing compounds with different pharmacological profiles from 7-OH itself. Some analogues have shown enhanced MOR selectivity, altered bias profiles, or modified pharmacokinetic properties. The goal of this research programme is to establish structure-activity relationships that could inform the design of novel analgesic compounds, not to produce modified consumer products.
3. Epidemiology and Consumer Use Patterns
Parallel to pharmacological research, a body of epidemiological and survey research has developed to understand who uses kratom, why, and with what reported outcomes. Published surveys have consistently found that a substantial proportion of kratom users report using it as a self-managed substitute for opioid medications or illicit opioids, as a self-management tool for opioid withdrawal symptoms, or for pain management.
These self-report surveys face significant methodological limitations: they rely on volunteer samples (typically online communities), cannot verify diagnoses or prior use histories, and are subject to recall and social desirability bias. They nonetheless represent important data on how kratom is actually being integrated into patterns of use outside clinical settings.
4. Adverse Event Analysis and Clinical Case Reports
A literature of adverse event reports and clinical case reports has developed in parallel with mechanistic research. These include reports of kratom-associated hepatotoxicity (liver injury), cardiac effects, and withdrawal syndromes following cessation of heavy use.
Interpreting adverse event reports presents well-known methodological challenges: reports are typically of single cases or small series, often involve polypharmacy, frequently lack biological sample data sufficient to confirm kratom alkaloid concentrations, and are subject to reporting biases. A systematic 2021 review noted that most reported kratom-associated fatalities involved concurrent use of other substances, making it difficult to attribute causation to kratom alone. These limitations do not mean adverse events should be dismissed, case reports serve an important signal-generating function in pharmacovigilance. They mean the evidence requires careful contextualisation.
5. Kratom and the Treatment Gap
Perhaps the most policy-relevant research question is whether kratom is playing a meaningful role in addressing the opioid treatment gap, the large proportion of individuals with opioid use disorder who do not access formal treatment. Survey research has found that kratom users frequently report using it as a self-managed substitute for opioids or as a tool for managing withdrawal. Whether this represents harm reduction or an exchange of one problematic substance for another is a genuinely contested empirical and ethical question that the current evidence base cannot resolve.
Methodological Challenges Facing the Field
Researchers working on kratom alkaloids face several distinctive methodological challenges that are important to understand when evaluating published findings:
- Source material variability: Natural kratom leaf material varies substantially in alkaloid composition, making replication of research using whole-plant material inherently difficult
- Reference standard availability: Certified reference standards for less-studied kratom alkaloids are not uniformly available, limiting multi-alkaloid characterisation in some laboratories
- Human clinical data scarcity: The regulatory environment for human clinical trials involving Schedule I candidate compounds creates barriers to conducting the clinical studies that would resolve many key uncertainties
- Self-report data limitations: Much of the epidemiological literature relies on self-reported use data from online communities, which are not representative of all kratom users
- Polypharmacy in adverse event reports: The majority of serious kratom-associated adverse events in the literature involve concurrent substance use, complicating causal attribution
Where the Field Is Heading
As of 2025, the trajectory of kratom alkaloid research appears to be moving in several directions simultaneously. Mechanistic pharmacology is advancing through synthetic analogue programmes and improved understanding of opioid receptor signalling. Epidemiological research is increasingly using larger, more representative samples and longitudinal designs. Clinical pharmacokinetic research is beginning to provide the human data that preclinical studies cannot generate.
Regulatory science is also developing, the question of what evidentiary standard should be applied to scheduling decisions for substances like kratom, where consumer use is widespread and the evidence is mixed, is itself becoming a recognised methodological challenge in drug policy research.
What the current moment represents is a field in genuine scientific motion, where important questions remain open, where new methods are being applied, and where the answers that emerge over the next several years are likely to substantially reshape the regulatory and clinical landscape. Accurately characterising where the science stands, rather than overstating or understating certainty, is the appropriate response to that situation.