Chemical composition and biological effects of kratom (Mitragyna speciosa): In vitro studies with implications for efficacy and drug interactions

Opioid system and related ligands: from the past to future perspectives

Chronic pain is a pathological condition affecting about 30% of population. It represents a relevant social-health issue worldwide, and it is considered a significant source of human suffering and disability, strongly affecting patients' quality of life. Despite several pharmacological strategies to guarantee an adequate pain management have been proposed over the years, opioids still represent one of the primary choices for treating moderate-to-severe pain in both cancer and non-cancer patients. However, chronic use of opioids often leads to numerous side effects, including respiratory depression, constipation, analgesic tolerance, and opioid-induced hyperalgesia (OIH), which can strongly limit their use. Given the fundamental role of opioid system in pain relief, this review provides a general overview about the main actors (endogenous opioid peptides and receptors) involved in its modulation. Furthermore, this review explores the action and the limitations of conventional clinically used opioids and describes the efficacy and safety profile of some promising analgesic compounds. A deeper understanding of the molecular mechanisms behind both analgesic effects and adverse events could advance knowledge in this field, thus improving chronic pain treatment.

Chemical, pharmacological properties and biosynthesis of opioid mitragynine in Mitragyna speciosa (kratom)

Mitragynine, an alkaloid found in Mitragyna speciosa (kratom), shows promise as a potential alternative to opioids owing to its distinctive indole alkaloid structure and its capacity for pain relief, alleviation of opioid withdrawal symptoms, and anti-inflammatory effects. Recently the intricate process of mitragynine biosynthesis from the precursor strictosidine was elucidated, providing insights into the complex pathways responsible for synthesizing this opioid compound and its related diastereomers. As the search continues for the authentic hydroxylase and methyltransferase crucial for mitragynine formation, leveraging enzymes from other species and exploiting enzyme promiscuity has facilitated heterologous mitragynine biosynthesis in microbes. This highlights the extraordinary flexibility of enzymes in generating a spectrum of variations and analogs of kratom opioids within alternative biological systems.

Kratom use and mental health: A systematic literature review and case example

OBJECTIVE

This review aims to synthesize and critically evaluate the existing literature on kratom use and its possible association with induction of psychotic and manic symptoms, in order to identify potential areas for future research that would improve our understanding of the risks of kratom consumption.

METHODS

An electronic search was performed using five major databases: including PubMed, Scopus, Google Scholar, Web of Science, and PsycINFO. keywords such as kratom, Mitragyna speciosa, mania, psychosis, bipolar disorder, schizophrenia, schizoaffective, case report, and case series. The retrieved articles on initial search were screened based on predefined inclusion and exclusion criteria for this study, and then data synthesis was performed to analyze relevant information from the included studies.

RESULTS

Six prior papers were found using (1 case series and 5 case reports). These included 10 cases, involving kratom use association with mania and psychosis. The ages of patients ranged from 28 to 55 years mean age was 38, and (SD 13.74), the majority were males (8 out of 11). Patients had durations of kratom use ranging from 2 wk to 15 years. Significant association was found between kratom use and the worsening of psychotic and manic symptoms in individuals with psychiatric conditions.

CONCLUSIONS

Our research highlights the possibility of worsening preexisting psychiatric conditions in the context of kratom use. This study emphasizes the need for clinical evaluation of patients for kratom use. Additional research is required to gain a deeper understanding of the potential mental health implications of kratom use, especially among vulnerable populations.

Beneficial and adverse health effects of kratom (Mitragyna speciosa): A critical review of the literature

Used in Southeast Asia for generations, kratom gained popularity in the United States and elsewhere over the past several decades. Derived from Mitragyna speciosa, kratom preparations including leaves, teas, powders, capsules, and extracts may yield stimulant, analgesic, and opioid-like effects that occur dose-dependently based on concentrations of kratom's key alkaloids, mitragynine and 7-hydroxymitragynine. Such effects are responsible for kratom's potential as a reduced-harm alternative to opiates and as a withdrawal treatment. But these properties are also associated with tolerance development and addictive potential. Given mitragynine and 7-hydroxymitragynine activity on cytochrome P450 isoforms and opioid receptors, adverse effects among polysubstance users are a concern. Current literature on the toxicology of kratom is reviewed, including product alkaloid concentrations, in vitro and in vivo data, epidemiological evidence, and human case data. The potential harms and benefits of kratom products are discussed within an exposure assessment framework, and recommendations for industry are presented. Current evidence indicates that kratom may have therapeutic potential in some persons and that products present few risks with typical, non-polysubstance use. However, few studies identified alkaloid doses at which adverse effects were expected in humans or animals. Such research is needed to inform future assessments of kratom's risks and benefits.

Electrical breakdown in liquid-phase processing on an enhancement of 7-hydroxymitragynine conversion from mitragynine in Mitragyna speciose (Kratom)

This study investigates the impact of the Electrical Breakdown in Liquid-phase (EBL) process on alkaloid transformation in Mitragyna speciose (Kratom) leaves, focusing on the conversion of mitragynine (MG) to 7-hydroxy mitragynine (7-OH-MG) by using advanced oxidation processes (AOPs). A novel reactor has been developed to enhance plasma exposure to Kratom leaf powdered solutions during the EBL process. Two distinct electrical voltage characteristics, half-positive and negative half-waves, have been utilized for the EBL, with an output voltage of 4.57 kVpeak at a no-load condition and a frequency of 50 Hz. The experimental findings demonstrate a time-dependent enhancement in the transformation process. The highest yield of 7-OH-MG, reaching 2,485 ± 134 μg/g of dried Kratom leaves weight, has been attained with the EBL processing generated by positive half-wave voltage after 20 min of EBL exposure. Notably, the EBL processing generated by positive half-wave voltage has outperformed the one generated by negative half-wave voltage by a significant factor of 2.01.

[Kratom-From natural remedy to addictive drug and back]

BACKGROUND

Kratom/ketum is a psychoactive herbal preparation that has been used for a long time as a remedy and performance-enhancing substance in Southeast Asia. The advancement of globalization is making kratom increasingly more available in the western world, where it is becoming increasingly more used.

OBJECTIVE

The current research on kratom and its ingredients is presented.

MATERIAL AND METHODS

An overview of the use and effects of kratom is exemplary given on the basis of reports. The instrumentalization of the drug and its consequences up to the development of addiction are discussed.

RESULTS

Consumption is accompanied by several instrumentalizeable effects so that kratom is used as a therapeutic substance in the self-management of pain, anxiety and depression as well as other substance addictions. Another benefit comes from the performance-enhancing effects on physical work and in a social context. Consumption is usually well controlled, rarely escalates and has few and mostly mild aversive side effects. The danger arises from consumption particularly when there is an escalation of the dose and from mixed consumption with other psychoactive substances. The main alkaloid mitragynine and the more potent 7‑hydroxy-mitragynine are considered mainly responsible for the effect. Both have a complex pharmacology that involves partial µ‑opioid receptor agonism.

DISCUSSION

Epidemiological, clinical and neurochemical studies have shown that kratom only has a limited addictive drug profile, which might suggest a medical use as a remedy or substitute in addiction treatment.

Associations Between Opioid and Kratom Use in the USA: Differences by Race/Ethnicity and Sexual Orientation

BACKGROUND

Kratom is federally unregulated and is marketed as an opioid alternative despite limited evidence and known negative effects. Disparities in associations between opioid and kratom use may be partly attributed to race/ethnicity and sexual orientation given differences in marketing, use motives, and prescriber practices.

METHODS

Data: 2021 nationally representative National Survey on Drug Use and Health among individuals aged 18 + . We used weighted logistic regression analyses to assess race/ethnicity and sexual orientation as moderators of associations between past-year opioid (1) use (total sample, n = 44,877) and (2) misuse and use disorder (among those with past-year opioid use, n = 10,398) and the outcome of kratom use (lifetime, past year).

RESULTS

26.76% reported past-year opioid use, and among those, 12.20% and 7.54% reported past-year opioid misuse and use disorder, respectively; 1.72% and 0.67% had lifetime and past-year kratom use, respectively. Opioid use was positively associated with lifetime (aOR = 2.69, 95%CI = 1.98, 3.66) and past-year (aOR = 3.84, 95%CI = 2.50, 5.92) kratom use; associations among non-Hispanic Black and Hispanic (vs. non-Hispanic White) participants were weaker (p < 0.01). Among participants reporting past-year opioid use, misuse and use disorder were positively associated with lifetime (aORmisuse = 2.46, 95%CI = 1.60, 3.78; aORuse disorder = 5.58, 95%CI = 2.82, 11.04) and past-year (aORmisuse = 2.40, 95%CI = 1.26, 4.59; aORuse disorder = 3.08, 95%CI = 1.48, 6.41) kratom use; among bisexual (vs. heterosexual) participants, opioid use disorder was associated with a lower probability of lifetime kratom use (p < 0.01).

DISCUSSION

We observed positive associations between opioid and kratom use, with potential disparities among certain racial/ethnic and sexual orientation groups. Research should examine the mechanisms contributing to these differences to inform prevention and intervention efforts.

Psychoactive plant derivatives (ayahuasca, ibogaine, kratom) and their application in opioid withdrawal and use disorder - a narrative review

The opioid epidemic and limited access to treatment for opioid withdrawal (OW) and opioid use disorder (OUD) has led individuals to seek alternative treatments. This narrative review aims to educate clinicians on the mechanisms of action, toxicity, and applications of psychoactive plant-based substances patients may be using to self-treat OUD and OW. We specifically discuss ayahuasca, ibogaine, and kratom as they have the most evidence for applications in OUD and OW from the last decade (2012-2022). Evidence suggests these substances may have efficacy in treating OW and OUD through several therapeutic mechanisms including their unique pharmacodynamic effects, rituals performed around ingestion, and increased neuroplasticity. The current evidence for their therapeutic application in OUD and OW is primarily based on small observational studies or animal studies. High-quality, longitudinal studies are needed to clarify safety and efficacy of these substances in treatment of OW and OUD.

Kratom (Mitragyna speciosa) Use and Mental Health: A Systematic Review and Multilevel Meta-Analysis

INTRODUCTION

Kratom (Mitragyna speciosa) is a medicinal tree native to Southeast Asia. The present multilevel meta-analysis describes the association between kratom use and the positive and negative indicators of mental health.

METHODS

A total of thirty-six articles were included in the meta-analysis to examine the associations, using a random-effects model.

RESULTS

The pooled effect size showed a very small positive association between kratom use and negative indicators of mental health {r = 0.092, 95% confidence interval (CI) = [0.020, 0.164], p < 0.05}, while no significant association was found with positive indicators of mental health (r = -0.031, 95% CI = [-0.149, 0.087], p > 0.05). Pooled effect sizes of specific mental health outcomes indicated that kratom use showed only a small positive correlation with externalizing disorders (r = 0.201, 95% CI = [0.107, 0.300], p < 0.001). No significant association was found between kratom use and quality of life (r = 0.069, 95% CI = [-0.104, 0.242], p > 0.05) and internalizing disorders (r = -0.001, 95% CI = [-0.115, 0.095], p > 0.05). Multilevel moderator analysis showed that the pooled effect size of the association between kratom use and substance use disorder was stronger in Malaysia (r = 0.347, 95% CI = [0.209, 0.516], p < 0.001), and with the mean age (β1 = -0.035, 95% CI = [-0.055, -0.014], p = 0.003), and the drug profile of those who were not co-using other drugs (r = 0.347, 95% CI = [0.209, 0.516], p < 0.001).

CONCLUSION

The meta-analysis supports the kratom instrumentalization concept, in that a positive gain from kratom consumption can be achieved without any significant adverse associations with mental health.

Phytochemical analysis of water and ethanol liquid extracts prepared using freshly harvested leaves of Mitragyna speciosa (Korth.)

Mitragyna speciosa, also known as kratom, has been reported to have a broad range of pharmacological properties. Freshly harvested leaves and their water extracts are consumed in Southeast Asia while preparations made from dried leaf material are consumed in Western countries. Our study evaluated the phytochemical composition of freshly harvested kratom leaves using LCMS/MS analysis of water and ethanol liquid extracts. Mitragynine and its congeners, including 7-hydroxymitragynine, speciocilliatine, speciogynine, paynantheine, as well as bioactive phenolics including chlorogenic acid, o-coumaric acid, quercitrin, and rutin were identified. However, 7-hydroxymitragynine was detected solely in the water-liquid extract. Currently, unknown compounds were also present in the chromatograms and mass spectra. The study results support that 7-hydroxymitragynine is a post-harvest oxidative derivative or metabolite of mitragynine. Further rigorous and comprehensive evaluations of the phytochemical composition of freshly harvested kratom leaves utilising advanced spectrometric methods are needed to establish the full spectrum of phytochemicals within the plant.

Kratom safety and toxicology in the public health context: research needs to better inform regulation

Although kratom use has been part of life for centuries in Southeast Asia, the availability and use of kratom in the United States (US) increased substantially since the early 2000s when there was little information on kratom pharmacology, use patterns, and effects, all critical to guiding regulation and policy. Here we provide a synthesis of research with several hundred English-language papers published in the past 5 years drawing from basic research, epidemiological and surveillance data, and recent clinical research. This review of available literature aims to provide an integrated update regarding our current understanding of kratom's benefits, risks, pharmacology, and epidemiology, which may inform United States-based kratom regulation. Recent surveillance indicates there are likely several million past-year kratom consumers, though estimates vary widely. Even without precise prevalence data, kratom use is no longer a niche, with millions of United States adults using it for myriad reasons. Despite its botanical origins in the coffee tree family and its polypharmacy, kratom is popularly characterized as an opioid with presumed opioid-system-based risks for addiction or overdose. Neuropharmacology, toxicology, and epidemiology studies show that kratom is more accurately characterized as a substance with diverse and complex pharmacology. Taken together the work reviewed here provides a foundation for future scientific studies, as well as a guide for ongoing efforts to regulate kratom. This work also informs much-needed federal oversight, including by the United States Food and Drug Administration. We conclude with recommendations for kratom regulation and research priorities needed to address current policy and knowledge gaps around this increasingly used botanical product.

The Complexities of Kratom: Insights on an Increasingly Frequent Clinical Encounter

Mitragyna speciosa (kratom) is a tropical tree native to Southeast Asia with dose-dependent stimulant and opioid properties. Kratom has garnered attention due to its increasing popularity and potential for dependence, tolerance, and withdrawal. We report the case of a 72-year-old man admitted to the hospital for a deep vein thrombosis and obstructive uropathy who began experiencing kratom withdrawal. He experienced less cravings and improvement in withdrawal symptoms with buprenorphine-naloxone 8 mg/2 mg daily. Notably, our case highlights kratom's contributions to a medically complex presentation and potential kratom-drug interactions due to its posited inhibitory effect on cytochrome P450 enzymes and P-glycoprotein. Our case adds to the growing literature which describes buprenorphine-naloxone as an effective treatment for kratom dependence and withdrawal.

A Platform for the Synthesis of Corynantheine-Type Corynanthe Alkaloids

Corynantheine-type alkaloids are major components of the Mitragyna speciosa, also known as kratom, that exhibit unique pharmacological activity. However, no universal method to prepare these alkaloids has been reported. Disclosed herein is a catalytic, asymmetric platform that enables rapid access to corynantheine alkaloids. The first enantioselective total synthesis of (-)-corynantheidine pseudoindoxyl is described. The first asymmetric syntheses of (+)-corynoxine and (-)-corynoxine B were also achieved, along with enantioselective syntheses of (-)-corynantheidol and (-)-corynantheidine. Through this work, all series of corynantheine alkaloids including indole, spirooxindole, and pseudoindoxyl can now be accessed in the laboratory, enabling comprehensive biological investigation of kratom alkaloids to be undertaken.

Effects of mitragynine on viability, proliferation, and migration of C6 rat glioma, SH-SY5Y human neuroblastoma, and HT22 immortalized mouse hippocampal neuron cell lines

Mitragynine (MG) is an indole alkaloid found in the extract of Mitragyna speciosa Korth native to Southeast Asia. Although MG is known for its pain-relieving and psychoactive effects, reports have suggested that it has therapeutic potential against neoplasms and psychiatric disorders. However, no evidence currently exists to support the effect of MG on brain tumors. This study aimed to investigate the antitumor effects of MG in C6 rat glioma and SH-SY5Y human neuroblastoma tumor cell lines compared with those in the non-tumor HT22 mouse hippocampal neuronal cell line. MTT assay for cell viability, clonogenic and wound healing assays for cell migration, Hoechst 33342/propidium iodide staining for nuclear morphology, and cell cycle distribution using flow cytometry were performed. MG at 125.47 μM (50 μg/ml) significantly reduced the viability of all cell lines, and the clonogenicity of C6 glioma cells began decreasing at 75.28 μM (30 μg/ml) of MG. Cell migration was inhibited in C6 and HT22 cells treated with 75.28 μM (30 μg/ml) of MG. Apoptotic nuclear condensation and fragmentation were observed in all cell lines treated with 125.47 μM (50 μg/ml) MG, whereas late-phase apoptotic cells were predominant in the group treated with 250.94 μM (100 μg/ml) of MG. The cell cycle assay results suggest that MG arrested the S phase in the C6 cell line and the G2/M phase in the HT22 cell lines. This study showed that MG induces cell death and cell cycle arrest, disrupting cell migration and reducing the clonogenicity of brain tumor cells.

Discovering Dynamic Plant Enzyme Complexes in Yeast for Kratom Alkaloid Pathway Identification

Discovering natural product biosynthetic pathways of medicinal plants is challenging and laborious. Capturing the coregulation patterns of pathway enzymes, particularly transcriptomic regulation, has proven an effective method to accelerate pathway identification. In this study, we developed a yeast-based screening method to capture the protein-protein interactions (PPI) between plant enzymes, which is another useful pattern to complement the prevalent approach. Combining this method with plant multiomics analysis, we discovered four enzyme complexes and their organized pathways from kratom, an alkaloid-producing plant. The four pathway branches involved six enzymes, including a strictosidine synthase, a strictosidine β-D-glucosidase (MsSGD), and four medium-chain dehydrogenase/reductases (MsMDRs). PPI screening selected six MsMDRs interacting with MsSGD from 20 candidates predicted by multiomics analysis. Four of the six MsMDRs were then characterized as functional, indicating the high selectivity of the PPI screening method. This study highlights the opportunity of leveraging post-translational regulation features to discover novel plant natural product biosynthetic pathways.

Evaluation of Antibacterial, Antibiofilm, Antioxidant, and Anti-Inflammatory Activities of Kratom Leaves (Mitragyna speciosa) Fermentation Supernatant Containing Lactobacillus rhamnosus GG

Kratom (Mitragyna speciosa) leaves are commonly used to enhance endurance and treat various diseases. This study evaluated the effect of kratom leaf fermentation with Lactobacillus rhamnosus. Antibacterial activity was investigated against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Escherichia coli, and E. coli O157:H7. Biofilm inhibition and eradication assays were also performed. Antioxidant properties were determined by measuring the total phenolic and flavonoid content and DPPH and ABTS scavenging activities. Nitric oxide and TNF-α, IL-1β, and IL-6 expressions in LPS-stimulated RAW 264.7 macrophage cells were also measured. Aqueous kratom extract exhibited promising effects against free radicals and pro-inflammatory cytokines. Notably, all fermented kratoms showed significant antibacterial activity against the tested pathogens and antibiofilm formation by S. aureus and MRSA. Furthermore, the eradication of established biofilms of fermented kratoms was observed in S. aureus (day 2, 50 mg/mL) and E. coli (day 2, 100 mg/mL and day 4, 50 mg/mL). To the best of our knowledge, this study is the first to report that fermented and non-fermented kratoms could be nutraceutical sources of antibacterial, antibiofilm, antioxidant, and anti-inflammatory substances against related diseases and can be applied further in dietary or cosmetic products with health-promoting effects.

Molecular insights into GPCR mechanisms for drugs of abuse

Substance abuse is on the rise, and while many people may use illicit drugs mainly due to their rewarding effects, their societal impact can range from severe, as is the case for opioids, to promising, as is the case for psychedelics. Common with all these drugs' mechanisms of action are G protein-coupled receptors (GPCRs), which lie at the center of how these drugs mediate inebriation, lethality, and therapeutic effects. Opioids like fentanyl, cannabinoids like tetrahydrocannabinol, and psychedelics like lysergic acid diethylamide all directly bind to GPCRs to initiate signaling which elicits their physiological actions. We herein review recent structural studies and provide insights into the molecular mechanisms of opioids, cannabinoids, and psychedelics at their respective GPCR subtypes. We further discuss how such mechanistic insights facilitate drug discovery, either toward the development of novel therapies to combat drug abuse or toward harnessing therapeutic potential.

A Pilot Study of the Striatal Dopamine Transporter Levels in Kratom-Dependent and Normal Subjects Using 99mTc-TRODAT-1 Single Photon Emission Computed Tomography-Computed Tomography (SPECT-CT)

OBJECTIVE

The study aims to elucidate the effects of kratom addiction on dopamine transporter (DAT) using [2-[[2-[[[3-(4-chlorophenyl)-8-methyl-8-azabicyclo[3.2.1]oct-2-yl]methyl](2-mercaptoethyl)amino]ethyl]amino]ethanethiolato(3-)-N2,N20,S2,S20]oxo-[1R-(exo-exo)]-[99mTc] technetium (99mTc-TRODAT-1) brain single photon emission computed tomography-computed tomography (SPECT-CT) in kratom-dependent and healthy subjects.

MATERIALS AND METHODS

We recruited 12 kratom-dependent subjects and 13 healthy men to participate in this study. Addiction, craving, depression, and cognitive scores were assessed. All subjects received a single bolus injection of 99mTc-TRODAT-1 with 914.1 MBq ± 65.5 of activity (mean ± SD). The brain SPECT-CT images were reconstructed using 3D ordered subset expectation maximization (3D-OSEM) along with attenuation correction (AC), scatter correction (SC), and resolution recovery (RR) with an iteration number of four and a subset of 10. The Cohen's Kappa interrater-reliability between two raters, the standardized uptake value of body weight (SUVBW), and the asymmetrical index percentage (AI%) were evaluated.

RESULTS

Kappa statistics showed a fine agreement of abnormal 99mTc-TRODAT-1 uptake in the striatum region for the kratom-dependent group with the κ value of 0.69 (p = 0.0001), and the percentage of agreement for rater 1 and rater 2 was 56% and 64%, respectively. There was a reduction in average SUV in kratom-dependent subjects compared to healthy control subjects in the left caudate and left striatum (0.938 vs. 1.251, p = 0.014, and 1.055 vs. 1.29, p = 0.036, respectively). There was a significant difference in the AI% of the caudate region between the kratom-dependent group and the normal group (33% vs. 14%, p = 0.019).

CONCLUSION

Our findings signify that kratom addiction, may cause a change in DAT level and the results can be confirmed using 99mTc-TRODAT-1 SPECT-CT.

Examining the Psychoactive Differences between Kratom Strains

Kratom (Mitragyna speciosa) is a Southeast Asian plant containing various alkaloids that induce pharmacological effects in humans. In Western countries, online vendors sell a variety of different kratom strains which are marketed to have distinct effect profiles. However, as of yet such marketing claims are unsubstantiated, and therefore the current study investigated whether differently colored kratom products can induce distinct effects, as self-reported by users. Six hundred forty-four current kratom users were anonymously surveyed to compare the self-reported effects of and motivations for using kratom products sold as red, green, and white strains. Most of the survey respondents were customers of the same kratom vendor, the products of which had been analyzed for their alkaloid content by an independent laboratory. The survey respondents reported distinct subjective experiences for different kratom strains, in a manner congruent with common marketing descriptions. However, the product analyses revealed no significant cross-strain differences in alkaloid content, suggesting that the reported effect differences might be disproportionally influenced by marketing narratives and anecdotal reports. Future studies should engage a more diverse population and include kratom strains from various vendors. Controlled, blinded experiments could assess whether the reported effect differences stem from a placebo effect or from alternative factors, e.g., minor alkaloids and terpenes.

Description of Kratom Exposure Events in Wisconsin as Reported to the Wisconsin Poison Center, January 1, 2010 to September 1, 2022

BACKGROUND

Consumption of kratom (Mitragyna speciosa), an herbal substance, can result in adverse health effects. We characterized kratom-associated adverse events in Wisconsin to provide pertinent recommendations for clinicians and public health practitioners.

METHODS

Using Wisconsin Poison Center data, we searched for and summarized all records associated with exposure to "kratom," "electronic delivery device containing kratom," or "mitragyna" from January 1, 2010, to September 1, 2022.

RESULTS

Kratom-associated exposure calls to the Wisconsin Poison Center increased 3.75 times during 2016 - 2020. Among all 59 calls, 26 (44.1%) reported concomitant use of another substance, agitation was the most common symptom reported (n = 23, 39%), and 7 persons required critical care. Three unintentional ingestions were reported in children aged less than 2 years old.

DISCUSSION

Kratom-associated exposure calls to the Wisconsin Poison Center generally have been increasing in frequency since 2011. Wisconsinites who choose to use kratom might benefit from education regarding health risks and safe storage practices to avoid unintentional pediatric exposure.

Metabolite and Molecular Characterization of Mitragyna speciosa Identifies Developmental and Genotypic Effects on Monoterpene Indole and Oxindole Alkaloid Composition

The monoterpene indole alkaloid (MIA) mitragynine has garnered attention as a potential treatment for pain, opioid use disorder, and opioid withdrawal because of its combined pharmacology at opioid and adrenergic receptors in humans. This alkaloid is unique to Mitragyna speciosa (kratom), which accumulates over 50 MIAs and oxindole alkaloids in its leaves. Quantification of 10 targeted alkaloids from several tissue types and cultivars of  M. speciosa revealed that mitragynine accumulation was highest in leaves, followed by stipules and stems, but was absent, along with other alkaloids, in roots. While mitragynine is the predominant alkaloid in mature leaves, juvenile leaves accumulate higher amounts of corynantheidine and speciociliatine. Interestingly, corynantheidine has an inverse relationship with mitragynine accumulation throughout leaf development. Characterization of various cultivars of M. speciosa indicated altered alkaloidal profiles ranging from undetectable to high levels of mitragynine. DNA barcoding and phylogenetic analysis using ribosomal ITS sequences revealed polymorphisms leading M. speciosa cultivars having lower mitragynine content to group with other mitragyna species, suggesting interspecific hybridization events. Root transcriptome analysis of low- and high-mitragynine-producing cultivars indicated significant differences in gene expression and revealed allelic variation, further supporting that hybridization events may have impacted the alkaloid profile of M. speciosa.

Antidiabetic and antioxidant activities of Mitragyna speciosa (kratom) leaf extract in type 2 diabetic rats

Mitragyna speciosa is a medicinal plant with a reputation for treating pains, diabetes as well as increasing energy and sexual desires. However, there is no scientific evidence to validate the antidiabetic effect of M. speciosa. This study investigated the antidiabetic effects of M. speciosa (Krat) ethanolic extract on fructose and streptozocin (STZ)-induced type 2 diabetic rats. In vitro antioxidant and antidiabetic effects were evaluated using DPPH, ABST, FRAP and α-glucosidase inhibitory assays. Rats with fructose/STZ induced T2D were treated with Krat (100 and 400 mg/kg) or metformin (200 mg/kg) for 5 weeks via oral gavage. Krat showed good antioxidant activity and also displayed potent α-glucosidase inhibitory activity. Administration of Krat to the diabetic rats significantly improved body weight gain, restored alterations in blood glucose level, glucose tolerance, dyslipidemia (increased cholesterol, triglycerides, low-density lipoprotein-cholesterol and reduced high-density lipoprotein), hepatorenal biomarkers alterations (alanine transaminase, aspartate transaminase, alanine phosphatase, creatinine and blood urea nitrogen) and oxidative stress indices (superoxide dismutase, glutathione and malondialdehyde)in the treated diabetic rats. Furthermore, Krat also restored pancreatic histological and increased immunohistochemical aberrations in the diabetic rats. These results for the first time demonstrated the antidiabetic and antihyperlipidemic potentials of M. speciosa, thus providing scientific reinforcement for the traditional use of the plant in the treatment of diabetes.

Directed Biosynthesis of Mitragynine Stereoisomers

Mitragyna speciosa ("kratom") is used as a natural remedy for pain and management of opioid dependence. The pharmacological properties of kratom have been linked to a complex mixture of monoterpene indole alkaloids, most notably mitragynine. Here, we report the central biosynthetic steps responsible for the scaffold formation of mitragynine and related corynanthe-type alkaloids. We illuminate the mechanistic basis by which the key stereogenic center of this scaffold is formed. These discoveries were leveraged for the enzymatic production of mitragynine, the C-20 epimer speciogynine, and fluorinated analogues.

An evaluation of adverse drug reactions and outcomes attributed to kratom in the US Food and Drug Administration Adverse Event Reporting System from January 2004 through September 2021

Kratom is a widely used Asian botanical that has gained popularity in the United States due to a perception that it can treat pain, anxiety, and opioid withdrawal symptoms. The American Kratom Association estimates 10-16 million people use kratom. Kratom-associated adverse drug reactions (ADRs) continue to be reported and raise concerns about the safety profile of kratom. However, studies are lacking that describe the overall pattern of kratom-associated adverse events and quantify the association between kratom and adverse events. ADRs reported to the US Food and Drug Administration Adverse Event Reporting System from January 2004 through September 2021 were used to address these knowledge gaps. Descriptive analysis was conducted to analyze kratom-related adverse reactions. Conservative pharmacovigilance signals based on observed-to-expected ratios with shrinkage were estimated by comparing kratom to all other natural products and drugs. Based on 489 deduplicated kratom-related ADR reports, users were young (mean age 35.5 years), and more often male (67.5%) than female patients (23.5%). Cases were predominantly reported since 2018 (94.2%). Fifty-two disproportionate reporting signals in 17 system-organ-class categories were generated. The observed/reported number of kratom-related accidental death reports was 63-fold greater than expected. There were eight strong signals related to addiction or drug withdrawal. An excess proportion of ADR reports were about kratom-related drug complaints, toxicity to various agents, and seizures. Although further research is needed to assess the safety of kratom, clinicians and consumers should be aware that real-world evidence points to potential safety threats.

Seasonal and Geographic Variation in Alkaloid Content of Kratom (Mitragyna speciosa (Korth.) Havil.) from Thailand

The objective of this study was to obtain data on the distribution of alkaloids in kratom plants grown in Thailand. Two collections were performed, covering the southern, central, and northern regions of Thailand and different seasons. The contents of alkaloids, including mitragynine (MG), paynantheine (PAY), and speciogynine (SG), were determined using the validated HPLC method. The 134 samples in the first collection were collected from Nam Phu subdistrict, Ban Na San, Surat Thani, Thailand, during June and October 2019 and January 2020. The maximum mitragynine content was 4.94% w/w in June (late summer), and the minimum content was 0.74% w/w in October (rainy season). To expand the study area after kratom decriminalization, 611 samples were collected in June-August 2021, October-December 2021, and January-April 2022. The accumulation of MG ranged from 0.35 to 3.46% w/w, 0.31 to 2.54% w/w, and 0.48 to 2.81% w/w, respectively. The meteorological data supported the climate's effect on alkaloid production. Soil analysis revealed the importance of Ca and Mg in promoting alkaloid production. Geographical locations played a role in the variation of MG in kratom leaves, but did not affect the color of leaf veins. In conclusion, the present study suggested that the alkaloid content in kratom diverges based on seasonal and geographical origin.

Biased Agonism: Lessons from Studies of Opioid Receptor Agonists

In ligand bias different agonist drugs are thought to produce distinct signaling outputs when activating the same receptor. If these signaling outputs mediate therapeutic versus adverse drug effects, then agonists that selectively activate the therapeutic signaling pathway would be extremely beneficial. It has long been thought that μ-opioid receptor agonists that selectively activate G protein- over β-arrestin-dependent signaling pathways would produce effective analgesia without the adverse effects such as respiratory depression. However, more recent data indicate that most of the therapeutic and adverse effects of agonist-induced activation of the μ-opioid receptor are actually mediated by the G protein-dependent signaling pathway, and that a number of drugs described as G protein biased in fact may not be biased, but instead may be low-intrinsic-efficacy agonists. In this review we discuss the current state of the field of bias at the μ-opioid receptor and other opioid receptor subtypes.

Discovering dynamic plant enzyme complexes in yeast for novel alkaloid pathway identification from a medicinal plant kratom

Discovering natural product biosynthetic pathways from medicinal plants is challenging and laborious, largely due to the complexity of the transcriptomics-driven pathway prediction process. Here we developed a novel approach that captures the protein-level connections between enzymes for pathway discovery with improved accuracy. We proved that heterologous protein-protein interaction screening in yeast enabled the efficient discovery of both dynamic plant enzyme complexes and the pathways they organize. This approach discovered complexes and pathways in the monoterpene indole alkaloid metabolism of a medicinal plant, kratom with high success rate. Screening using a strictosidine β-D-glucosidase (MsSGD1) against 19 medium-chain dehydrogenase/reductases (MsMDRs) identified five MsSGD1-MsMDR complexes. Three out of the five interacting MsMDRs were then proven functional, while the remaining 14 non-interacting candidates did not show obvious activities. The work discovered three branched pathways by combining transcriptomics, metabolomics, and heterologous PPI screening and demonstrated a new plant pathway discovery strategy.

How Low Can You Go? Selecting Intensity Thresholds for Untargeted Metabolomics Data Preprocessing

Untargeted mass spectrometry (MS) metabolomics is an increasingly popular approach for characterizing complex mixtures. Recent studies have highlighted the impact of data preprocessing for determining the quality of metabolomics data analysis. The first step in data processing with untargeted metabolomics requires that signal thresholds be selected for which features (detected ions) are included in the dataset. Analysts face the challenge of knowing where to set these thresholds; setting them too high could mean missing relevant features, but setting them too low could result in a complex and unwieldy dataset. This study compared data interpretation for an example metabolomics dataset when intensity thresholds were set at a range of feature heights. The main observations were that low signal thresholds (1) improved the limit of detection, (2) increased the number of features detected with an associated isotope pattern and/or an MS-MS fragmentation spectrum, and (3) increased the number of in-source clusters and fragments detected for known analytes of interest. When the settings of parameters differing in intensities were applied on a set of 39 samples to discriminate the samples through principal component analyses (PCA), similar results were obtained with both low- and high-intensity thresholds. We conclude that the most information-rich datasets can be obtained by setting low-intensity thresholds. However, in the cases where only a qualitative comparison of samples with PCA is to be performed, it may be sufficient to set high thresholds and thereby reduce the complexity of the data processing and amount of computational time required.

Narrative Review of Kratom, an Emerging Psychoactive Substance With Perianesthetic Implications

Opioid overprescribing, with resultant overdose and death, has led to a national focus on alternative treatments for pain. With the decline in legal access to opioids, kratom has gained popularity as a legal, "natural," and easily accessible nonprescription analgesic for consumers wishing to self-medicate for pain, opioid use disorder, and other mental health conditions. While implications of kratom use in patients with chronic pain and/or opioid use disorder have been published, information on perianesthetic implications is lacking. Anesthesiologists should be informed about kratom, including the potential for unexpected physiologic derangements and adverse drug interactions resulting from complex pharmacologic activity, cytochrome P450 interactions, and common adulterations of the drug that may result in unpredictable clinical effects. This article explores the relevance of kratom to perioperative anesthetic care, including suggestions for anesthesiologists extrapolated from published information in nonoperative settings that may improve patient safety in individuals using kratom.

Social, psychological, and substance use characteristics of U.S. adults who use kratom: Initial findings from an online, crowdsourced study

Kratom, a plant that produces opioid-like effects, has gained popularity in the U.S. for self-treating symptoms of chronic pain, mood disorders, and substance-use disorders (SUDs). Most data on kratom are from surveys into which current kratom-using adults could self-select; such surveys may underrepresent people who have used kratom and chosen to stop. Available data also do not adequately assess important psychosocial factors surrounding kratom use. In this study, U.S. adults who reported past 6-month alcohol, opioid, and/or stimulant use (N = 1,670) were recruited via Amazon Mechanical Turk between September and December 2020. Of the 1,510 evaluable respondents, 202 (13.4%) reported lifetime kratom use. Kratom-using adults, relative to others, were typically younger, male, unpartnered, without children, and had lower income. They had higher rates of chronic pain (31.7% vs. 21.9%, p = .003), childhood adversity, anxiety, and depression (p < .001), and lower perceived social rank (d = .19, .02-.22) and socioeconomic status (d = .37 .16-.26). They also reported higher use rates for most substances (except alcohol); this included medically supervised and unsupervised use of prescription opioids and diverted opioid agonist therapy (OAT) medications. Most (83.2%) met diagnostic criteria for any past-year SUD. Those reporting kratom use were less likely to reside in an urban/suburban area. The strongest predictors of kratom use were use of other drugs: cannabidiol (OR = 3.73), psychedelics (OR = 3.39), and nonmedical prescription opioids (OR = 1.72). Another strong predictor was lifetime OAT utilization (OR = 2.31). Despite seemingly poorer psychosocial functioning and health among respondents reporting lifetime kratom use, use of other substances may be the strongest indicators of kratom use. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Associations of Lifetime Nonmedical Opioid, Methamphetamine, and Kratom Use within a Nationally Representative US Sample

Co-use of non-medical opioids (NMO) and methamphetamine is increasing. So too is the use of the psychoactive botanical "kratom," including among people with NMO and methamphetamine use histories. We assessed characteristics associated with respondent groups who reported lifetime methamphetamine and/or kratom use within a nationally representative US sample using 2019 National Survey on Drug Use and Health data from respondents reporting lifetime NMO use (diverted prescription opioids, heroin). Weighted prevalence estimates for demographic, mental health, and substance use outcomes were determined. Logistic regression examined associations between group membership and outcomes. Among this sample of respondents with lifetime NMO use, 67.6% (95% CI = 65.6-69.4%) reported only NMO use; 4.6% (3.9-5.4%) reported NMO+Kratom; 24.7% (22.7-26.7%) reported NMO+Methamphetamine; and 3.2% (2.5-3.9%) reported NMO+Methamphetamine+Kratom. Compared to those in the NMO-only group, the NMO+Kratom group was more likely to report past-year serious mental illness (SMI; OR = 2.27), suicidality (OR = 1.89), and past-month psychological distress (OR = 1.88). The NMO+Methamphetamine+Kratom group was more likely to report past-year SMI (OR = 2.65), past-month psychological distress (OR = 2.06), and unmet mental health needs (OR = 2.03); increased odds for drug injection, opioid withdrawal, and perceived treatment need also emerged. Risk factors were observed for all groups but were greatest among those reporting use of all three substances.

Variations in mitragynine content in the naturally growing Kratom (Mitragyna speciosa) population of Thailand

We analyzed the content of mitragynine (MG) found in kratom leaves (Mitragyna speciosa) and the influence of different environmental conditions (air and soil variables) on the yield in various regions of Thailand. The content of MG in kratom leaves ranged from 7.5 - 26.6 mg g^-1 of dry leaf weight. Canonical correspondence analysis showed that the most significant environmental variables affecting the MG content among the various regions were light intensity, relative humidity, soil volumetric water content (VW), soil pH, and calcium. This study is a first step towards providing information about environmental conditions suitable to maximize the quality and quantity of bioactive alkaloids in kratom. Future studies should focus on leaf collection and the post-harvest processes in order to assure the desired alkaloidal content in finished products, when produced under suitable environmental conditions identified in this study.

Kratom use categories and their associations with co-occurring substance use and mental health disorder symptoms during the COVID-19 pandemic

BACKGROUND

Kratom, a psychoactive substance, use is an evolving research area that needs more studies to augment the limited literature. Our study examines the association between kratom use categories and mental health and substance use disorders in the U.S.

METHODS

We used the 2020 National Survey on Drug Use and Health data (N = 32,893), a cross-sectional survey data, on the U.S. population aged 12 years or older. We used STATA/SE version 16 to perform a multinomial logistic regression analysis to assess our study aims.

RESULTS

Bisexuals, compared to heterosexuals, had higher risks of kratom use within the past 30 days (relative risk ratio [RRR]= 2.47, 95% CI= 1.07, 5.71). Major depressive episode was positively associated with kratom use more than 30 days ago (RRR= 2.04, 95% CI= 1.24, 3.34). This association was also observed for mild (RRR= 2.04, 95% CI= 1.38, 3.02), moderate (RRR= 2.25, 95% CI= 1.13, 4.51), or severe alcohol use disorder (RRR= 1.88, 95% CI= 1.05, 3.36); and mild (RRR= 1.98, 95% CI= 1.27, 3.11), moderate (RRR= 2.38, 95% CI= 1.27, 4.45), or severe marijuana use disorder (RRR= 2.13, 95% CI= 1.02, 4.47). Illicit drug other than marijuana use disorder was associated positively with kratom use more than 30 days ago (RRR= 2.81, 95% CI= 1.85, 4.26) and kratom use within the past 30 days (RRR= 5.48, 95% CI= 1.50, 20.02).

CONCLUSIONS

Our findings suggested that identifying as bisexual, experiencing depression, alcohol use disorder, or illicit drug use disorder increased the risks of kratom use. There is a need to consider mental health and substance use disorders and sexual identity in kratom use interventions and policies geared toward reducing or preventing kratom use.

Kratom: Substance of Abuse or Therapeutic Plant?

Kratom is the common term for Mitragyna speciosa and its products. Its major active compounds are mitragynine and 7-hydroxymitragynine. An estimated 2.1 million US residents used kratom in 2020, as a "legal high" and self-medication for pain, opioid withdrawal, and other conditions. Up to 20% of US kratom users report symptoms consistent with kratom use disorder. Kratom use is associated with medical toxicity and death. Causality is difficult to prove as almost all cases involve other psychoactive substances. Daily, high-dose use may result in kratom use disorder and opioid-like withdrawal on cessation of use. These are best treated with buprenorphine.

Kratom (Mitragyna speciosa) Validation: Quantitative Analysis of Indole and Oxindole Alkaloids Reveals Chemotypes of Plants and Products

Many consumers are turning to kratom (Mitragyna speciosa) to self-manage pain and opioid addiction. In the United States, an array of capsules, powders, and loose-leaf kratom products are readily available. Additionally, several online sites supply live kratom plants. A prerequisite to establishing quality control and quality assurance standards for the kratom industry, or understanding how alkaloid levels effect clinical outcomes, is the identification and quantitation of major and minor alkaloid constituents within available products and preparations. To this end, an ultra-high performance liquid chromatography-high resolution mass spectrometry method was developed for the analysis of 8 indole alkaloids (7-hydroxymitragynine, ajmalicine, paynantheine, mitragynine, speciogynine, isopaynantheine, speciociliatine, and mitraciliatine) and 6 oxindole alkaloids (isomitraphylline, isospeciofoleine, speciofoline, corynoxine A, corynoxeine, and rhynchophylline) in US-grown kratom plants and commercial products. These commercial products shared a qualitatively similar alkaloid profile, with 12 - 13 detected alkaloids and high levels of the indole alkaloid mitragynine (13.9 ± 1.1 - 270 ± 24 mg/g). The levels of the other major alkaloids (paynantheine, speciociliatine, speciogynine, mitraciliatine, and isopaynantheine) and the minor alkaloids varied in concentration from product to product. The alkaloid profile of US-grown M. speciosa "Rifat" showed high levels of the indole alkaloid speciogynine (7.94 ± 0.83 - 11.55 ± 0.18 mg/g) and quantifiable levels of isomitraphylline (0.943 ± 0.033 - 1.47 ± 0.18 mg/g). Notably, the alkaloid profile of a US-grown M. speciosa seedling was comparable to the commercial products with a high level of mitragynine (15.01 ± 0.20 mg/g). This work suggests that there are several M. speciosa chemotypes.

Metabolism of Speciociliatine, an Overlooked Kratom Alkaloid for its Potential Pharmacological Effects

Speciociliatine, a diastereomer of mitragynine, is an indole-based alkaloid found in kratom (Mitragyna speciosa). Kratom has been widely used for the mitigation of pain and opioid dependence, as a mood enhancer, and/or as an energy booster. Speciociliatine is a partial µ-opioid agonist with a 3-fold higher binding affinity than mitragynine. Speciociliatine has been found to be a major circulating alkaloid in humans following oral administration of a kratom product. In this report, we have characterized the metabolism of speciociliatine in human and preclinical species (mouse, rat, dog, and cynomolgus monkey) liver microsomes and hepatocytes. Speciociliatine metabolized rapidly in monkey, rat, and mouse hepatocytes (in vitro half-life was 6.6 ± 0.2, 8.3 ± 1.1, 11.2 ± 0.7 min, respectively), while a slower metabolism was observed in human and dog hepatocytes (91.7 ± 12.8 and > 120 min, respectively). Speciociliatine underwent extensive metabolism, primarily through monooxidation and O-demethylation metabolic pathways in liver microsomes and hepatocytes across species. No human-specific or disproportionate metabolites of speciociliatine were found in human liver microsomes. The metabolism of speciociliatine was predominantly mediated by CYP3A4 with minor contributions by CYP2D6.

Development and validation of a gradient HPLC-UV method for mitragynine following in vitro skin permeation studies

Mitragynine is a promising candidate for pain relief and opiate replacement but the investigations for drug delivery are lacking. This study aims to investigate the potential of mitragynine to be delivered through the skin with an emphasis on developing and validating a gradient HPLC-UV analytical method to determine mitragynine in the samples collected during in vitro skin permeation studies. The optimised method involves a gradient elution using a C18 column with a mobile phase comprising acetonitrile and 0.1 %v/v of formic acid (0-1 min: 30:70 to 70:30 (v/v) and hold up to 4 min; 4-6 min: return to 30:70 (v/v) and hold up to 10 min) at a flow rate of 1.2 mL/min. This method was validated based on the standards set by the International Council on Harmonisation guidelines. The method showed mitragynine elution at ∼ 4 min with adequate linearity (R2 ≥ 0.999 for concentration ranges of 0.5-10 and 10-175 μg/mL) and acceptable limits of detection and quantification at 0.47 and 1.43 μg/mL, respectively. The analytical performance is robust with excellent precision and accuracy. This method was used to evaluate the in vitro skin permeation of mitragynine (5 %w/v) from simple solvent systems over 48 hr. The results showed a cumulative amount of mitragynine permeated at ∼ 11 μg/cm2 for dimethyl sulfoxide and ∼ 4 μg/cm2 for propylene glycol. The study not only addressed the issues of the currently available HPLC-UV methods that limit the direct application but also affirmed the potential of mitragynine to be delivered through the skin.

Understanding Kratom Use: A Guide for Healthcare Providers

Kratom (Mitragyna speciosa Korth., Rubiaceae) is a plant native to Southeast Asia, where it has been used for centuries as a mild stimulant and as medicine for various ailments. More recently, as kratom has gained popularity in the West, United States federal agencies have raised concerns over its safety leading to criminalization in some states and cities. Some of these safety concerns have echoed across media and broad-based health websites and, in the absence of clinical trials to test kratom’s efficacy and safety, considerable confusion has arisen among healthcare providers. There is, however, a growing literature of peer-reviewed science that can inform healthcare providers so that they are better equipped to discuss kratom use with consumers and people considering kratom use within the context of their overall health and safety, while recognizing that neither kratom nor any of its constituent substances or metabolites have been approved as safe and effective for any disease. An especially important gap in safety-related science is the use of kratom in combination with physiologically active substances and medicines. With these caveats in mind we provide a comprehensive overview of the available science on kratom that has the potential to i clarity for healthcare providers and patients. We conclude by making recommendations for best practices in working with people who use kratom.

Searching for a Signal: Self-Reported Kratom Dose-Effect Relationships Among a Sample of US Adults With Regular Kratom Use Histories

There is limited understanding regarding kratom use among US adults. Although motivations for use are increasingly understood, typical kratom doses, threshold of (low and high) doses for perceived effectiveness, and effects produced during cessation are not well documented. We aimed to extend prior survey work by recruiting adults with current and past kratom exposure. Our goal was to better understand kratom dosing, changes in routines, and perception of effects, including time to onset, duration, and variability of beneficial and adverse outcomes from use and cessation. Among respondents who reported experiencing acute kratom effects, we also sought to determine if effects were perceived as helpful or unhelpful in meeting daily obligations. Finally, we attempted to detect any signal of a relationship between the amount of kratom consumed weekly and weeks of regular use with ratings of beneficial effects from use and ratings of adverse effects from cessation. We conducted an online survey between April-May 2021 by re-recruiting participants from a separate study who reported lifetime kratom use. A total of 129 evaluable surveys were collected. Most (59.7%) had used kratom >100 times and reported currently or having previously used kratom >4 times per week (62 weeks on average). Under half (41.9%) reported that they considered themselves to be a current "regular kratom user." A majority (79.8%) reported experiencing acute effects from their typical kratom dose and that onset of effects began in minutes but dissipated within hours. Over a quarter reported that they had increased their kratom dose since use initiation, whereas 18.6% had decreased. Greater severity of unwanted effects from ≥1 day of kratom cessation was predicted by more weeks of regular kratom use (β = 6.74, p = 0.02). Acute kratom effects were largely reported as compatible with, and sometimes helpful in, meeting daily obligations. In the absence of human laboratory studies, survey methods must be refined to more precisely assess dose-effect relationships. These can help inform the development of controlled observational and experimental studies needed to advance the public health understanding of kratom product use.

The respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine

Background and Purpose

Mitragynine, the major alkaloid in Mitragyna speciosa (kratom), is a partial agonist at the μ opioid receptor. CYP3A‐dependent oxidation of mitragynine yields the metabolite 7‐OH mitragynine, a more efficacious μ receptor agonist. While both mitragynine and 7‐OH mitragynine can induce anti‐nociception in mice, recent evidence suggests that 7‐OH mitragynine formed as a metabolite is sufficient to explain the anti‐nociceptive effects of mitragynine. However, the ability of 7‐OH mitragynine to induce μ receptor‐dependent respiratory depression has not yet been studied.

Experimental Approach

Respiration was measured in awake, freely moving, male CD‐1 mice, using whole body plethysmography. Anti‐nociception was measured using the hot plate assay. Morphine, mitragynine, 7‐OH mitragynine and the CYP3A inhibitor ketoconazole were administered orally.

Key Results

The respiratory depressant effects of mitragynine showed a ceiling effect, whereby doses higher than 10 mg·kg⁻¹ produced the same level of effect. In contrast, 7‐OH mitragynine induced a dose‐dependent effect on mouse respiration. At equi‐depressant doses, both mitragynine and 7‐OH mitragynine induced prolonged anti‐nociception. Inhibition of CYP3A reduced mitragynine‐induced respiratory depression and anti‐nociception without affecting the effects of 7‐OH mitragynine.

Conclusions and Implications

Both the anti‐nociceptive effects and the respiratory depressant effects of mitragynine are partly due to its metabolic conversion to 7‐OH mitragynine. The limiting rate of conversion of mitragynine into its active metabolite results in a built‐in ceiling effect of the mitragynine‐induced respiratory depression. These data suggest that such ‘metabolic saturation’ at high doses may underlie the improved safety profile of mitragynine as an opioid analgesic.

Clinical Pharmacokinetic Assessment of Kratom (Mitragyna speciosa), a Botanical Product with Opioid-like Effects, in Healthy Adult Participants

Increasing use of the botanical kratom to self-manage opioid withdrawal and pain has led to increased kratom-linked overdose deaths. Despite these serious safety concerns, rigorous fundamental pharmacokinetic knowledge of kratom in humans remains lacking. We assessed the pharmacokinetics of a single low dose (2 g) of a well-characterized kratom product administered orally to six healthy participants. Median concentration-time profiles for the kratom alkaloids examined were best described by a two-compartment model with central elimination. Pronounced pharmacokinetic differences between alkaloids with the 3S configuration (mitragynine, speciogynine, paynantheine) and alkaloids with the 3R configuration (mitraciliatine, speciociliatine, isopaynantheine) were attributed to differences in apparent intercompartmental distribution clearance, volumes of distribution, and clearance. Based on noncompartmental analysis of individual concentration-time profiles, the 3S alkaloids exhibited a shorter median time to maximum concentration (1–2 vs. 2.5–4.5 h), lower area under the plasma concentration-time curve (430–490 vs. 794–5120 nM × h), longer terminal half-life (24–45 vs. ~12–18 h), and higher apparent volume of distribution during the terminal phase (960–12,700 vs. ~46–130 L) compared to the 3R alkaloids. Follow-up mechanistic in vitro studies suggested differential hepatic/intestinal metabolism, plasma protein binding, blood-to-plasma partitioning, and/or distribution coefficients may explain the pharmacokinetic differences between the two alkaloid types. This first comprehensive pharmacokinetic characterization of kratom alkaloids in humans provides the foundation for further research to establish safety and effectiveness of this emerging botanical product.

Kratom Abuse Potential 2021: An Updated Eight Factor Analysis

Drugs are regulated in the United States (US) by the Controlled Substances Act (CSA) if assessment of their abuse potential, including public health risks, show such control is warranted. An evaluation via the 8 factors of the CSA provides the comprehensive assessment required for permanent listing of new chemical entities and previously uncontrolled substances. Such an assessment was published for two kratom alkaloids in 2018 that the Food and Drug Administration (FDA) have identified as candidates for CSA listing: mitragynine (MG) and 7-hydroxymitragynine (7-OH-MG) (Henningfield et al., 2018a). That assessment concluded the abuse potential of MG was within the range of many other uncontrolled substances, that there was not evidence of an imminent risk to public health, and that a Schedule I listing (the only option for substances that are not FDA approved for therapeutic use such as kratom) carried public health risks including drug overdoses by people using kratom to abstain from opioids. The purpose of this review is to provide an updated abuse potential assessment reviewing greater than 100 studies published since January 1, 2018. These include studies of abuse potential and physical dependence/withdrawal in animals; in-vitro receptor binding; assessments of potential efficacy treating pain and substance use disorders; pharmacokinetic/pharmacodynamic studies with safety-related findings; clinical studies of long-term users with various physiological endpoints; and surveys of patterns and reasons for use and associated effects including dependence and withdrawal. Findings from these studies suggest that public health is better served by assuring continued access to kratom products by consumers and researchers. Currently, Kratom alkaloids and derivatives are in development as safer and/or more effective medicines for treating pain, substances use disorders, and mood disorders. Placing kratom in the CSA via scheduling would criminalize consumers and possession, seriously impede research, and can be predicted to have serious adverse public health consequences, including potentially thousands of drug overdose deaths. Therefore, CSA listing is not recommended. Regulation to minimize risks of contaminated, adulterated, and inappropriately marketed products is recommended.

How essential is kratom availability and use during COVID-19? Use pattern analysis based on survey and social media data

Background: Kratom, a tree native to Southeast Asia, is increasingly used in Western countries for self-treatment of pain, psychiatric disorders, and mitigation of withdrawal symptoms from drugs of abuse. Because kratom is solely supplied from its native locations, supply shortages during the COVID-19 pandemic may impact the availability of preparations and hence force consumers to change their patterns of use. The aim of this study was to understand if and how COVID-19 was influencing kratom purchasing and use. Methods: Additional questions specific to kratom availability and changes in use during COVID-19 were added to an international online survey with responses collected between January and July 2020. During the same period, kratom-related social media posts to Twitter, Reddit, and Bluelight were analyzed for themes similar to the survey questions. Results: The survey results indicated no changes in kratom use patterns although the sample size was relatively small (n = 70) with younger consumers reporting a potential issue in obtaining their desired products from their usual sources. The survey respondents identified primarily as non-Hispanic whites (87.1%). Social media themes revolved primarily around quitting kratom during COVID-19, misinformation about the effects of kratom on COVID-19, and other non-COVID-related discussions. While some consumers may increase their kratom dose because of additional stress, a majority of discussions centered around reducing or rationing kratom due to COVID-19 or a perceived dependence. Access to quality kratom products was also a major discussion topic on social media. Conclusions: Kratom use patterns did not change due to COVID-19 but consumers were concerned about potential product shortages and resulting quality issues. Clinicians and public health officials need to be informed and educated about kratom use as a potential mitigation strategy for substance use disorders and for self-treatment of pain.

Respiratory effects of oral mitragynine and oxycodone in a rodent model

RATIONALE

Kratom derives from Mitragyna speciosa (Korth.), a tropical tree in the genus Mitragyna (Rubiaceae) that also includes the coffee tree. Kratom leaf powders, tea-like decoctions, and commercial extracts are taken orally, primarily for health and well-being by millions of people globally. Others take kratom to eliminate opioid use for analgesia and manage opioid withdrawal and use disorder. There is debate over the possible respiratory depressant overdose risk of the primary active alkaloid, mitragynine, a partial μ-opioid receptor agonist, that does not signal through ß-arrestin, the primary opioid respiratory depressant pathway.

OBJECTIVES

Compare the respiratory effects of oral mitragynine to oral oxycodone in rats with the study design previously published by US Food and Drug Administration (FDA) scientists for evaluating the respiratory effects of opioids (Xu et al., Toxicol Rep 7:188-197, 2020).

METHODS

Blood gases, observable signs, and mitragynine pharmacokinetics were assessed for 12 h after 20, 40, 80, 240, and 400 mg/kg oral mitragynine isolate and 6.75, 60, and 150 mg/kg oral oxycodone hydrochloride.

FINDINGS

Oxycodone administration produced significant dose-related respiratory depressant effects and pronounced sedation with one death each at 60 and 150 mg/kg. Mitragynine did not yield significant dose-related respiratory depressant or life-threatening effects. Sedative-like effects, milder than produced by oxycodone, were evident at the highest mitragynine dose. Maximum oxycodone and mitragynine plasma concentrations were dose related.

CONCLUSIONS

Consistent with mitragynine's pharmacology that includes partial µ-opioid receptor agonism with little recruitment of the respiratory depressant activating β-arrestin pathway, mitragynine produced no evidence of respiratory depression at doses many times higher than known to be taken by humans.

A systematic review of (pre)clinical studies on the therapeutic potential and safety profile of kratom in humans

INTRODUCTION

Kratom (Mitragyna speciosa) is a tropical plant traditionally used as an ethnomedicinal remedy for several conditions in South East Asia. Despite the increased interest in its therapeutical benefits in Western countries, little scientific evidence is available to support such claims, and existing data remain limited to kratom's chronic consumption.

OBJECTIVE

Our study aims to investigate (pre)clinical evidence on the efficacy of kratom as a therapeutic aid and its safety profile in humans.

METHODS

A systematic literature search using PubMed and the Medline database was conducted between April and November 2020.

RESULTS

Both preclinical (N = 57) and clinical (N = 18) studies emerged from our search. Preclinical data indicated a therapeutic value in terms of acute/chronic pain (N = 23), morphine/ethanol withdrawal, and dependence (N = 14), among other medical conditions (N = 26). Clinical data included interventional studies (N = 2) reporting reduced pain sensitivity, and observational studies (N = 9) describing the association between kratom's chronic (daily/frequent) use and safety issues, in terms of health consequences (e.g., learning impairment, high cholesterol level, dependence/withdrawal).

CONCLUSIONS

Although the initial (pre)clinical evidence on kratom's therapeutic potential and its safety profile in humans is encouraging, further validation in large, controlled clinical trials is required.

For Better or Worse: Self-reported Changes in Kratom and Other Substance Use as a Result of the COVID-19 Pandemic

Background:

Kratom is taken to self-treat pain and symptoms of psychiatric disorders, including substance-use disorders (SUDs) and opioid withdrawal. Before COVID-19, kratom use was increasing in the US, however, there are few published data on whether that trend continued during the COVID-19 pandemic, which could have affected kratom use in multiple ways.

Aim:

To examine COVID-19-related changes in kratom use and how these changes were experienced, relative to changes in other commonly used substances.

Methods:

Using Amazon Mechanical Turk, 2615 evaluable surveys were completed between September 2020 and March 2021. Responses from past-month and past-year kratom-using adults (N = 174) indicating changes for the better or worse were examined using generalized linear mixed effects models, and relevant open-text responses (n = 85) were thematically coded.

Results:

For kratom 33% (n = 58) reported a Covid-related increase and 24% (n = 42) reported a Covid-related decrease. Controlling for changes in amount used, alcohol (OR = 5.02), tobacco (OR = 4.72), and nonmedical opioid use (OR = 3.42) were all more likely to have changed for the worse, compared with kratom use. Relative to decreases in kratom use, decreases in alcohol (OR = 3.21) and tobacco (OR = 6.18) use were more likely to be changes for the better. Cannabis use was the only substance to display a probability lower than 50% of being a decrease for the better, and of the increases, cannabis use displayed the highest probability of being for the better.

Conclusions:

Increases in kratom and cannabis use were less likely than alcohol and tobacco to be reported as changes for the worse, and decreases in kratom and cannabis use were more likely than alcohol and tobacco to be reported as changes for the better. These findings indicate that people differently conceptualize their relationships with kratom and cannabis, compared to their relationships with alcohol and tobacco.