Inhibitory effect of mitragynine on human cytochrome P450 enzyme activities

Inhibitory effects of Kratom constituents, mitragynine and 7-hydroxymitragynine, on 4-methylumbelliferone glucuronidation by human UDP-glucuronosyltransferases

As Kratom use increases, concerns about potential herb-drug interactions with liver enzymes, particularly UDP-glucuronosyltransferases (UGTs), have emerged. This study investigated the inhibitory effects of Kratom leaf constituents, mitragynine and 7-hydroxymitragynine, on 4-methylumbelliferone (4MU) glucuronidation by a panel of recombinant human UGT enzymes, including UGT1A1, UGT1A3, UGT1A6, UGT1A9, UGT2B7, and UGT2B15. The degree of inhibition exhibited by mitragynine and 7-hydroxymitragynine on UGTs varied. Mitragynine exhibited the highest inhibitory potency on UGT1A3 with an IC50 value of 72 µM. Moderate inhibition potency of mitragynine were observed for UGT1A6, UGT1A9 and UGT2B15, with IC50 value of 121, 131, and 152 µM, respectively, whereas the inhibition on UGT1A1 and UGT2B7 was low (IC50 > 200 µM). 7-Hydroxymitragynine exhibited the highest inhibitory potency on UGT1A9, with IC50 value of 51 µM, while moderate potency was observed for UGT1A1 and UGT1A3, with IC50 value of 196 and 141 µM, respectively. The inhibitory potency of 7-hydroxymitragynine on UGT2B15 was low (IC50 > 200 µM), while negligible effects were observed for UGT1A6 and UGT2B7. Kinetic inhibition study revealed that mitragynine noncompetitively inhibited UGT1A3 (Ki = 45 µM) and competitively inhibited UGT1A9 (Ki = 114 µM), while 7-hydroxymitragynine competitively inhibited UGT1A3 (Ki = 33 µM) and noncompetitively inhibited UGT1A9 (Ki = 29 µM). The experimental Ki values found here are relatively high compared to the maximum plasma concentrations of mitragynine and 7-hydroxymitragynine reported in humans, suggesting an unlikely potential for herb-drug interactions via UGT inhibition.

Drug-drug interactions of plant alkaloids derived from herbal medicines on the phase II UGT enzymes: an introductory review

Herbal medicines are widely used as alternative or complementary therapies to treat and prevent chronic diseases. However, these can lead to drug-drug interactions (DDIs) that affect the glucuronidation reaction of UDP glucuronosyltransferases (UGTs), which convert drugs into metabolites. Plant extracts derived from medicinal herbs contain a diverse array of compounds categorized into different functional groups. While numerous studies have examined the inhibition of UGT enzymes by various herbal compounds, it remains unclear which group of compounds exerts the most significant impact on DDIs in the glucuronidation reaction. Recently, alkaloids derived from medicinal herbs, including kratom (Mitragyna speciosa), have gained attention due to their diverse pharmacological properties. This review primarily focuses on the DDIs of plant alkaloids from medicinal herbs, including kratom on the phase II UGT enzymes. Kratom is a new emerging herbal product in Western countries that is often used to self-treat chronic pain, opioid withdrawal, or as a replacement for prescription and non-prescription opioids. Kratom is well-known for its psychoactive alkaloids, which have a variety of psychopharmacological effects. However, the metabolism mechanism of kratom alkaloids, particularly on the phase II pathway, is still poorly understood. Simultaneously using kratom or other herbal products containing alkaloids with prescribed medicines may have an impact on the drug metabolism involving the phase II UGT enzymes. To ensure the safety and efficacy of treatments, gaining a better understanding of the DDIs when using herbal products with conventional medicine is crucial.

An in vitro evaluation on metabolism of mitragynine to 9-O-demethylmitragynine

Kratom (Mitragyna Speciosa Korth.) is an indigenous tree native to Southeast Asia whose leaves have been traditionally ingested as a tea and has seen its popularity increase in the United States. Although kratom and its constituents presently have no approved uses by the Food and Drug Administration, its major alkaloids (e.g., mitragynine) have psychoactive properties that may hold promise for the treatment of opioid cessation, pain management, and other indications. 9-O-demethylmitragynine is a major metabolite formed from mitragynine metabolism (36 % total metabolism) and displays similar pharmacologic activity. Cytochrome P450 (CYP) 3A4 has been identified as a major enzyme involved in mitragynine metabolism; however, the in vitro metabolism parameters of 9-O-demethylmitragynine formation are not well defined and a risk of potential drug interactions exists. Using human liver S9 fractions, 9-O-demethylmitragynine formation was generally linear for enzyme concentrations of 0-0.25 mg/mL and incubation times of 5-20 min. 9-O-demethylmitragynine displayed a Km 1.37 μM and Vmax of 0.0931 nmol/min/mg protein. Known CYP inhibitors and compounds that might be concomitantly used with kratom were assessed for inhibition of 9-O-demethylmitragynine formation. Ketoconazole, a CYP3A index inhibitor, demonstrated a significant effect on 9-O-demethylmitragynine formation, further implicating CYP3A4 as a major metabolic pathway. Major cannabinoids (10 μg/mL) displayed minor inhibition of 9-O-demethylmitragynine formation, while all other compounds had minimal effects. Mixtures of physiological achievable cannabinoid concentrations also displayed minor effects on 9-O-demethylmitragynine formation, making a metabolic drug interaction unlikely; however, further in vitro, in vivo, and clinical studies are necessary to fully exclude any risk.

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.

Kratom-Induced Psychiatric Decompensation and Paranoid Delusions

Kratom is a plant extract readily available for purchase in the USA. It is known to produce both stimulant and opioid-related effects, predisposing it to abuse. The long-term effects of kratom are poorly understood. In rare cases, serious side effects have been reported. Here, we report a case of a patient with a history of bipolar type schizoaffective disorder presenting with acute onset paranoia and delusions. The patient had been hospitalized seven times previously with psychotic symptoms, with no reported history of paranoid delusional thought content in previous admissions. It was discovered that the patient had been ingesting increasingly large quantities of kratom in the weeks leading up to the admission. It is believed that kratom may be responsible for the novel symptoms contributing to the patient's acute psychiatric decompensation.

An update on the clinical pharmacology of kratom: uses, abuse potential, and future considerations

INTRODUCTION

Kratom (Mitragyna speciosa) has generated substantial clinical and scientific interest as a complex natural product. Its predominant alkaloid mitragynine and several stereoisomers have been studied for activity in opioid, adrenergic, and serotonin receptors. While awaiting clinical trial results, the pre-clinical evidence suggests a range of potential therapeutic applications for kratom with careful consideration of potential adverse effects.

AREAS COVERED

The focus of this review is on the pharmacology, pharmacokinetics, and potential drug-drug interactions of kratom and its individual alkaloids. A discussion on the clinical pharmacology and toxicology of kratom is followed by a summary of user surveys and the evolving concepts of tolerance, dependence, and withdrawal associated with kratom use disorder.

EXPERT OPINION

With the increasing use of kratom in clinical practice, clinicians should be aware of the potential benefits and adverse effects associated with kratom. While many patients may benefit from kratom use with few or no reported adverse effects, escalating dose and increased use frequency raise the risk for toxic events in the setting of polysubstance use or development of a use disorder.

A Critical Review of the Neuropharmacological Effects of Kratom: An Insight from the Functional Array of Identified Natural Compounds

Kratom (Mitragyna speciosa Korth. Havil) has been considered a narcotic drug for years, barred by the law in many parts of the world, while extensive research over the past few decades proves its several beneficial effects, some of which are still in ambiguity. In many countries, including Thailand, the indiscriminate use and abuse of kratom have led to the loss of life. Nonetheless, researchers have isolated almost fifty pure compounds from kratom, most of which are alkaloids. The most prevalent compounds, mitragynine and 7-hydroxy mitragynine, are reported to display agonist morphine-like effects on human μ-opioid receptors and antagonists at κ- and δ-opioid receptors with multimodal effects at other central receptors. Mitragynine is also credited to be one of the modulatory molecules for the Keap1-Nrf2 pathway and SOD, CAT, GST, and associated genes' upregulatory cascades, leading it to play a pivotal role in neuroprotective actions while evidently causing neuronal disorders at high doses. Additionally, its anti-inflammatory, antioxidative, antibacterial, and gastroprotective effects are well-cited. In this context, this review focuses on the research gap to resolve ambiguities about the neuronal effects of kratom and demonstrate its prospects as a therapeutic target for neurological disorders associated with other pharmacological effects.

An in vitro evaluation of kratom (Mitragyna speciosa) on the catalytic activity of carboxylesterase 1 (CES1)

Kratom, (Mitragyna Speciosa Korth.) is a plant indigenous to Southeast Asia whose leaves are cultivated for a variety of medicinal purposes and mostly consumed as powders or tea in the United States. Kratom use has surged in popularity with the lay public and is currently being investigated for possible therapeutic benefits including as a treatment for opioid withdrawal due to the pharmacologic effects of its indole alkaloids. A wide array of psychoactive compounds are found in kratom, with mitragynine being the most abundant alkaloid. The drug-drug interaction (DDI) potential of mitragynine and related alkaloids have been evaluated for effects on the major cytochrome P450s (CYPs) via in vitro assays and limited clinical investigations. However, no thorough assessment of their potential to inhibit the major hepatic hydrolase, carboxylesterase 1 (CES1), exists. The purpose of this study was to evaluate the in vitro inhibitory potential of kratom extracts and its individual major alkaloids using an established CES1 assay and incubation system. Three separate kratom extracts and the major kratom alkaloids mitragynine, speciogynine, speciociliatine, paynantheine, and corynantheidine displayed a concentration-dependent reversible inhibition of CES1. The experimental Ki values were determined as follows for mitragynine, speciociliatine, paynantheine, and corynantheidine: 20.6, 8.6, 26.1, and 12.5 μM respectively. Speciociliatine, paynantheine, and corynantheidine were all determined to be mixed-type reversible inhibitors of CES1, while mitragynine was a purely competitive inhibitor. Based on available pharmacokinetic data, determined Ki values, and a physiologically based inhibition screen mimicking alkaloid exposures in humans, a DDI mediated via CES1 inhibition appears unlikely across a spectrum of doses (i.e., 2-20g per dose). However, further clinical studies need to be conducted to exclude the possibility of a DDI at higher and extreme doses of kratom and those who are chronic users.

Translating Kratom-Drug Interactions: From Bedside to Bench and Back

Kratom is a botanical natural product belonging to the coffee family, with stimulant effects at low doses and opioid-like effects at higher doses. During the last two decades, kratom has been purported as a safer alternative to pharmaceutical and illicit drugs to self-manage pain and opioid withdrawal symptoms. Kratom alkaloids, typically mitragynine, have been detected in biologic samples from overdose deaths. These deaths are often observed in combination with other drugs and are suspected to result from polyintoxications. This review focuses on the potential for kratom to precipitate pharmacokinetic interactions with object drugs involved in these reported polyintoxications. The legal status, chemistry, pharmacology, and toxicology are also summarized. The aggregate in vitro and clinical data identified kratom and select kratom alkaloids as modulators of cytochrome P450 (P450) enzyme activity, notably as inhibitors of CYP2D6 and CYP3A, as well as P-glycoprotein-mediated efflux activity. These inhibitory effects could increase the systemic exposure to co-consumed object drugs, which may lead to adverse effects. Collectively, the evidence to date warrants further evaluation of potential kratom-drug interactions using an iterative approach involving additional mechanistic in vitro studies, well designed clinical studies, and physiologically based pharmacokinetic modeling and simulation. This critical information is needed to fill knowledge gaps regarding the safe and effective use of kratom, thereby addressing ongoing public health concerns. SIGNIFICANCE STATEMENT: The botanical kratom is increasingly used to self-manage pain and opioid withdrawal symptoms due to having opioid-like effects. The legal status, chemistry, pharmacology, toxicology, and drug interaction potential of kratom are reviewed. Kratom-associated polyintoxications and in vitro-in vivo extrapolations suggest that kratom can precipitate pharmacokinetic drug interactions by inhibiting CYP2D6, CYP3A, and P-glycoprotein. An iterative approach that includes clinical studies and physiologically based pharmacokinetic modeling and simulation is recommended for further evaluation of potential unwanted kratom-drug interactions.

Kratom: History, pharmacology, current user trends, adverse health effects and potential benefits

Kratom (Mitragyna speciosa Korth.) is a tree native to Southeast Asia with dose-dependent stimulant and opioid-like effects. Dried, powdered leaf material is among the kratom products most commonly consumed in the US and Europe, but other formulations also exist including enriched extracts, resins, tinctures, and edibles. Its prevalence in the US remains debated and the use pattern includes self-treatment of mood disorders, pain, and substance use disorders. Most of the adverse effects of kratom and its alkaloid mitragynine have been reported in the literature as case reports or part of surveys necessitating confirmation by clinical trials. Toxicities associated with kratom consumption have focused on hepatic, cardiac, and CNS effects with the potential to cause fatalities primarily as part of polydrug exposures. Kratom may also present with drug-drug interactions primarily through CYP 3A4 and 2D6 inhibition, although the clinical significance remains unknown to date. The variability in composition of commercially available kratom products complicates generalization of findings and requires further investigation by employing clinical trials. Healthcare professionals should remain cautious in counseling patients on the use of kratom in a therapeutic setting.

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.

Controversial usages of kratom (Mitragyna speciosa): For good or for evil

Kratom (Mitragyna speciosa) is a plant that grows well in tropical climates such as in Southeast Asia. Traditionally, people discovered it possessed a stimulating effect that relieved tiredness. Furthermore, it contains analgesic and medicinal properties for the treatment of pain, diarrhea, muscle discomfort, and blood pressure and to enhance stamina. Nevertheless, long term or regular consumption of kratom leads to addiction. This is because the main alkaloid of kratom, mitragynine, binds to opioid receptors and exerts a euphoric effect similar to that of morphine, which may lead to death. Due to this reason, kratom has been listed as a regulated substance in many countries including the United States, Thailand, Malaysia, Bhutan, Finland, Lithuania, Denmark, Poland, Sweden, Australia, and Myanmar. Usages of kratom carry two pharmacological effects depending on dosage. Low-dose kratom exerts a stimulating effect that refreshes the user. High-dose kratom exerts sedative effects that can lead to addiction similar to that of morphine. Despite the euphoric effect of kratom, the beneficial values of kratom to human health is indisputable. Therefore, a complete banning of kratom may cause a loss to pharmaceutical industry. Rather, a controlled or selective usage of kratom will be a better choice.

Development and Validation of an HPLC-UV Method for the Quantification of 4'-Hydroxydiclofenac Using Salicylic Acid: Future Applications for Measurement of In Vitro Drug-Drug Interaction in Rat Liver Microsomes

Salicylic acid is a key compound in nonsteroidal anti-inflammatory drugs that has been recently used for preventing the risk of hospitalization and death among COVID-19 patients and in preventing colorectal cancer (CRC) by suppressing two key proteins. Understanding drug−drug interaction pathways prevent the occurrence of adverse drug reactions in clinical trials. Drug−drug interactions can result in the variation of the pharmacodynamics and pharmacokinetic of the drug. Inhibition of the Cytochrome P450 enzyme activity leads to the withdrawal of the drug from the market. The aim of this paper was to develop and validate an HPLC-UV method for the quantification of 4′-hydroxydiclofenac as a CYP2C9 metabolite using salicylic acid as an inhibitor in rat liver microsomes. A CYP2C9 assay was developed and validated on the reversed phase C18 column (SUPELCO 25 cm × 4.6 mm × 5 µm) using a low-pressure gradient elution programming at T = 30 °C, a wavelength of 282 nm, and a flow rate of 1 mL/min. 4′-hydroxydiclofenac demonstrated a good linearity (R2 > 0.99), good reproducibility, low detection, and quantitation limit, and the inter and intra-day precision met the ICH guidelines (<15%). 4′-hydroxydiclofenac was stable for three days and showed an acceptable accuracy and recovery (80−120%) within the ICH guidelines in a rat liver microsome sample. This method will be beneficial for future applications of the in vitro inhibitory effect of salicylic acid on the CYP2C9 enzyme activity in rat microsomes and the in vivo administration of salicylic acid in clinical trials.

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.

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.

Kratom Alkaloids: Interactions With Enzymes, Receptors, and Cellular Barriers

Parallel to the growing use of kratom, there is a wealth of evidence from self-report, preclinical, and early clinical studies on therapeutic benefits of its alkaloids in particular for treating pain, managing substance use disorder, and coping with emotional or mental health conditions. On the other hand, there are also reports on potential health risks concerning kratom use. These two aspects are often discussed in reviews on kratom. Here, we aim to highlight specific areas that are of importance to give insights into the mechanistic of kratom alkaloids pharmacological actions. This includes their interactions with drug-metabolizing enzymes and predictions of clinical drug-drug interactions, receptor-binding properties, interactions with cellular barriers in regards to barrier permeability, involvement of membrane transporters, and alteration of barrier function when exposed to the alkaloids.

Clinical Pharmacology of the Dietary Supplement, Kratom (Mitragyna speciosa)

Kratom (Mitragyna speciosa) consists of over 40 alkaloids with two of them, mitragynine (MG) and 7-OH-mitragynine (7-OH-MG) being the main psychoactive compounds. MG and 7-OH-MG each target opioid receptors and have been referred to as atypical opioids. They exert their pharmacologic effects on the μ, δ, and κ opioid receptors. In addition, they affect adrenergic, serotonergic, and dopaminergic pathways. Kratom has been touted as an inexpensive, legal alternative to standard opioid replacement therapy such as methadone and buprenorphine. Other uses for kratom include chronic pain, attaining a "legal high," and numerous CNS disorders including anxiety depression and post-traumatic stress disorder (PTSD). Kratom induces analgesia and mild euphoria with a lower risk of respiratory depression or adverse central nervous system effects compared to traditional opioid medications. Nonetheless, kratom has been associated with both physical and psychological dependence with some individuals experiencing classic opioid withdrawal symptoms upon abrupt cessation. Kratom use has been linked to serious adverse effects including liver toxicity, seizures, and death. These risks are often compounded by poly-substance abuse. Further, kratom may potentiate the toxicity of coadministered medications through modulation of cytochrome P450, P-glycoprotein, and uridine diphosphate glucuronosyltransferase enzymes (UGDT). In 2016 the U.S. Drug Enforcement Administration (DEA) took steps to classify kratom as a federal schedule 1 medication; however, due to public resistance, this plan was set aside. Until studies are conducted that define kratom's role in treating opioid withdrawal and/or other CNS conditions, kratom will likely remain available as a dietary supplement for the foreseeable future. This article is protected by copyright. All rights reserved.

The Adverse Cardiovascular Effects and Cardiotoxicity of Kratom (Mitragyna speciosa Korth.): A Comprehensive Review

Background: Kratom or Mitragyna speciosa (Korth.) has received overwhelming attention recently due to its alleged pain-relieving effects. Despite its potential therapeutic value, kratom use has been linked to many occurrences of multiorgan toxicity and cardiotoxicity. Accordingly, the current narrative review aimed to provide a detailed account of kratom's adverse cardiovascular effects and cardiotoxicity risk, based on in vitro studies, poison center reports, coroner and autopsy reports, clinical case reports, and clinical studies. Methods: An electronic search was conducted to identify all research articles published in English from 1950 to 2021 using the major research databases, such as Google Scholar, Web of Science, PubMed, Scopus, Mendeley, EMBASE, Cochrane Library, and Medline. We then analyzed the literature's discussion of adverse cardiovascular effects, toxicity, and mortality related to kratom use. Results: Our findings revealed that, although in vitro studies have found kratom preparations' most abundant alkaloid-mitragynine-to cause a prolonged QTc interval and an increased risk of torsades de pointes, a clinical study examining humans' regular consumption of kratom did not report such a risk. However, this latter study did show that regular kratom use could induce an increased QTc interval in a dose-dependent manner. A few case reports also highlighted that kratom consumption is associated with ventricular arrhythmia and cardiopulmonary arrest, but this association could have ensued when kratom was co-administered with another substance. Similarly, analyses of national poison data showed that kratom's most common adverse acute cardiovascular effects include tachycardia and hypertension. Meanwhile, coroner and autopsy reports indicated that kratom's cardiovascular sequelae encompass coronary atherosclerosis, myocardial infarction, hypertensive cardiovascular disease, left ventricular hypertrophy, cardiac arrhythmia, cardiomegaly, cardiomyopathy, focal band necrosis in the myocardium, and myocarditis. Given the available data, we deduced that all cardiac eventualities reported in the literature could have been compounded by polysubstance use and unresolved underlying medical illnesses. Conclusion: Although kratom use has been associated with death and cardiotoxicity, especially at higher doses and when associated with other psychoactive drugs, the dearth of data and methodological limitations reported in existing studies do not allow a definitive conclusion, and further studies are still necessary to address this issue.

Assessment of Cardiovascular Functioning Among Regular Kratom (Mitragyna speciosa Korth) Users: A Case Series

Multiorgan toxicities have been extensively reported in kratom (Mitragyna speciosa Korth) users in Western countries but not in Southeast Asia. Existing literature argued that this discrepancy may be due to underreporting of kratom-related toxicity cases in Southeast Asia. Hence, this case series filled the research gap by clinically assessing the cardiovascular functioning and serum mitragynine level of regular kratom users in its traditional settings in Malaysia. Nine regular kratom users without history of polysubstance use were recruited from the same community via snowball sampling and were subjected to electrocardiogram (ECG) and echocardiogram assessments. Serum mitragynine analysis was also performed by solid-phase extraction and liquid chromatography-tandem mass spectrometry. The mean serum mitragynine level was 10.3 mg/L (SD = 6.9) and ranged from 2.5 mg/L to 22.4 mg/L. Those who consumed an average daily quantity of four or more glasses of brewed kratom juice (p = 0.045) and those who had prolonged QTc intervals (p = 0.017) had significantly higher serum mitragynine level. Echocardiographic findings of all the respondents were normal except one reported left ventricular hypertrophy and another had trivial tricuspid regurgitation with pulmonary artery systolic pressure (PASP) of 10 + 5 mmHg. Regular kratom use without concomitant use of other illicit substances may not provoke any risk of cardiovascular impairment or toxicity except for prolonged QTc interval, which appeared to be dose dependent. However, as this study was limited by a small sample size, future studies with larger sample size are warranted to confirm our findings.

A Case Report of Kratom-Induced Psychosis

This case report details a patient with a complex medical history who was brought for psychiatric evaluation. An abrupt switch in Kratom use patterns was identified as the most likely causative factor of his symptoms. Adrenal insufficiency and posttraumatic stress disorder (PTSD) were considered both in the differential and potential confounding factors in his presentation. This paper discusses current Kratom use trends in the United States, the drug's legal status, and the common reasons patients may use it. Additionally, research gaps regarding the safety and efficacy of Kratom's use for self-medication are addressed.

Kratom: The safe legal high?

Illicit drugs are used to produce a sense of euphoria in the user. Like marijuana, kratom is a plant-based substance. The leaves of the Mitragyna speciosa tree were used to treat mild medical conditions in Thailand and Malaysia as a stimulant in low doses, and sedative and analgesic at high doses. Over recent years, kratom gained popularity as a recreational drug among younger individuals in Southeast Asia due to its availability as a cheap and easily assessable substance with euphoric effects. This trend has rapidly made its way to the West. Unlike marijuana, in the United States kratom's use as an inexpensive herbal recreational "supplement" is poorly popularized. However, emerging reports garnished from use as a recreational drug reveals a potential health hazard. Seizures and neurological consequences have been reported from kratom abuse. Complex pharmacokinetics place patients at further risk of side effects and drug interactions. Still, individuals can legally purchase kratom at stores and through online distributers in capsule form or as teas, powders, and extracts under the veil of a harmless herbal remedy. Without United States Food and Drug Administration oversight, kratom has a high potential for abuse and without regulatory control threatens public safety.

Refined Prediction of Pharmacokinetic Kratom-Drug Interactions: Time-Dependent Inhibition Considerations

Preparations from the leaves of the kratom plant (Mitragyna speciosa) are consumed for their opioid-like effects. Several deaths have been associated with kratom used concomitantly with some drugs. Pharmacokinetic interactions are potential underlying mechanisms of these fatalities. Accumulating in vitro evidence has demonstrated select kratom alkaloids, including the abundant indole alkaloid mitragynine, as reversible inhibitors of several cytochromes P450 (CYPs). The objective of this work was to refine the mechanistic understanding of potential kratom-drug interactions by considering both reversible and time-dependent inhibition (TDI) of CYPs in the liver and intestine. Mitragynine was tested against CYP2C9 (diclofenac 4'-hydroxylation), CYP2D6 (dextromethorphan O-demethylation), and CYP3A (midazolam 1'-hydroxylation) activities in human liver microsomes (HLMs) and CYP3A activity in human intestinal microsomes (HIMs). Comparing the absence to presence of NADPH during preincubation of mitragynine with HLMs or HIMs, an ∼7-fold leftward shift in IC50 (∼20 to 3 μM) toward CYP3A resulted, prompting determination of TDI parameters (HLMs: K I , 4.1 ± 0.9 μM; k inact , 0.068 ± 0.01 min-1; HIMs: K I , 4.2 ± 2.5 μM; k inact , 0.079 ± 0.02 min-1). Mitragynine caused no leftward shift in IC50 toward CYP2C9 (∼40 μM) and CYP2D6 (∼1 μM) but was a strong competitive inhibitor of CYP2D6 (K i , 1.17 ± 0.07 μM). Using a recommended mechanistic static model, mitragynine (2-g kratom dose) was predicted to increase dextromethorphan and midazolam area under the plasma concentration-time curve by 1.06- and 5.69-fold, respectively. The predicted midazolam area under the plasma concentration-time curve ratio exceeded the recommended cutoff (1.25), which would have been missed if TDI was not considered. SIGNIFICANCE STATEMENT: Kratom, a botanical natural product increasingly consumed for its opioid-like effects, may precipitate potentially serious pharmacokinetic interactions with drugs. The abundant kratom indole alkaloid mitragynine was shown to be a time-dependent inhibitor of hepatic and intestinal cytochrome P450 3A activity. A mechanistic static model predicted mitragynine to increase systemic exposure to the probe drug substrate midazolam by 5.7-fold, necessitating further evaluation via dynamic models and clinical assessment to advance the understanding of consumer safety associated with kratom use.

Development of a Physiologically Based Pharmacokinetic Model of Mitragynine, Psychoactive Alkaloid in Kratom (Mitragyna Speciosa Korth.), In Rats and Humans

Mitragynine is a major psychoactive alkaloid in leaves of kratom (Mitragyna speciosa Korth.). To understand its disposition in organs, this study aimed to develop a physiologically based pharmacokinetic (PBPK) model that predicts mitragynine concentrations in plasma and organ of interests in rats and humans. The PBPK model consisted of six organ compartments (i.e. lung, brain, liver, fat, slowly perfused tissues, and rapidly perfused tissue). From systematic searching, three pharmacokinetic studies of mitragynine (two studies in rats and 1 study in humans) were retrieved from the literature. Berkeley Madonna Software (version 8.3.18) was used for model development and model simulation. The developed PBPK model consisted of biologically relevant features following involvement of (i) breast cancer-resistant protein (BCRP) in brain, (ii) a hepatic cytochrome P450 3A4 (CYP3A4)-mediated metabolism in the liver, and (iii) a diffusion-limited transport in fat. The simulations adequately describe simulated and observed data in the two species with different dosing regimens. PBPK models of mitragynine in rats and humans were successfully developed. The models may be used to guide optimal mitragynine dosing regimens.

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

The safety and efficacy of kratom (Mitragyna speciosa) for treatment of pain is highly controversial. Kratom produces more than 40 structurally related alkaloids, but most studies have focused on just two of these, mitragynine and 7-hydroxymitragynine. Here, we profiled 53 commercial kratom products using untargeted LC-MS metabolomics, revealing two distinct chemotypes that contain different levels of the alkaloid speciofoline. Both chemotypes were confirmed with DNA barcoding to be M. speciosa. To evaluate the biological relevance of variable speciofoline levels in kratom, we compared the opioid receptor binding activity of speciofoline, mitragynine, and 7-hydroxymitragynine. Mitragynine and 7-hydroxymitragynine function as partial agonists of the human µ-opioid receptor, while speciofoline does not exhibit measurable binding affinity at the µ-, δ- or ƙ-opioid receptors. Importantly, mitragynine and 7-hydroxymitragynine demonstrate functional selectivity for G-protein signaling, with no measurable recruitment of β-arrestin. Overall, the study demonstrates the unique binding and functional profiles of the kratom alkaloids, suggesting potential utility for managing pain, but further studies are needed to follow up on these in vitro findings. All three kratom alkaloids tested inhibited select cytochrome P450 enzymes, suggesting a potential risk for adverse interactions when kratom is co-consumed with drugs metabolized by these enzymes.

A New Data Repository for Pharmacokinetic Natural Product-Drug Interactions: From Chemical Characterization to Clinical Studies

There are many gaps in scientific knowledge about the clinical significance of pharmacokinetic natural product-drug interactions (NPDIs) in which the natural product (NP) is the precipitant and a conventional drug is the object. The National Center for Complimentary and Integrative Health created the Center of Excellence for NPDI Research (NaPDI Center) (www.napdi.org) to provide leadership and guidance on the study of pharmacokinetic NPDIs. A key contribution of the Center is the first user-friendly online repository that stores and links pharmacokinetic NPDI data across chemical characterization, metabolomics analyses, and pharmacokinetic in vitro and clinical experiments (repo.napdi.org). The design is expected to help researchers more easily arrive at a complete understanding of pharmacokinetic NPDI research on a particular NP. The repository will also facilitate multidisciplinary collaborations, as the repository links all of the experimental data for a given NP across the study types. The current work describes the design of the repository, standard operating procedures used to enter data, and pharmacokinetic NPDI data that have been entered to date. To illustrate the usefulness of the NaPDI Center repository, more details on two high-priority NPs, cannabis and kratom, are provided as case studies. SIGNIFICANCE STATEMENT: The data and knowledge resulting from natural product-drug interaction (NPDI) studies is distributed across a variety of information sources, rendering difficulties to find, access, and reuse. The Center of Excellence for NPDI Research addressed these difficulties by developing the first user-friendly online repository that stores data from in vitro and clinical pharmacokinetic NPDI experiments and links them with study data from chemical characterization and metabolomics analyses of natural products that are also stored in the repository.

Is kratom (Mitragyna speciosa Korth.) use associated with ECG abnormalities? Electrocardiogram comparisons between regular kratom users and controls

OBJECTIVES

Little is known about the cardiotoxic effects of kratom (Mitragyna speciosa Korth.), a medicinal plant. This analytical cross-sectional study investigated the prevalence of electrocardiogram (ECG) abnormalities and QTc intervals in regular kratom users compared with non-kratom-using control subjects.

METHODS

We enrolled regular kratom users and non-kratom-using control subjects from three communities. Demographic data, clinical data, kratom use characteristics, and ECG findings were recorded. The mitragynine content of kratom juice was quantified using a validated gas chromatography-mass spectrometry (GC-MS) method.

RESULTS

A total of 200 participants (100 kratom users and 100 control subjects) participated in this study. The prevalence of ECG abnormalities in kratom users (28%) did not differ from that of control subjects (32%). Kratom use was not associated with ECG abnormalities, except for significantly higher odds of sinus tachycardia (OR = 8.61, 95% CI = 1.06-70.17, p = 0.035) among kratom users compared with control subjects. The odds of observing borderline QTc intervals were significantly higher for kratom users compared with control subjects, regardless of the age of first use, the duration of use, the daily quantity consumed, and the length of time that had elapsed between last kratom use and ECG assessment. Nevertheless, there were no differences in the odds of having prolonged QTc intervals between kratom users and controls. The estimated average daily intake of mitragynine consumed by kratom users was 434.28 mg.

CONCLUSION

We found no link between regular kratom use and electrocardiographic abnormalities with an estimated average daily intake of 434.28 mg of mitragynine.

Drug-Induced Liver Injury Caused by Kratom Use as an Alternative Pain Treatment Amid an Ongoing Opioid Epidemic

Kratom (Mitragyna speciosa) is a prevalent medicinal plant used mainly for the stimulant and analgesic properties provided through multiple alkaloid compounds. Over the past decade, use of kratom has increased despite the limited knowledge of toxicities and adverse side effects. With the current opioid epidemic, both patients and providers are seeking alternative methods to treat both addiction and pain control, and kratom as an alternative means of treatment has increasingly entered the mainstream. In this article, we present the clinical course of a 47-year-old male who developed fatigue, pruritus, and abnormal liver tests (with a mixed hepatocellular/cholestatic pattern) approximately 21 days after beginning kratom. After extensive evaluation including a negligible alcohol history, negative hepatitis serologies, and inconclusive imaging, the patient was diagnosed with drug-induced liver injury (DILI) caused by kratom. Nine months after his liver tests returned to normal, he took kratom again, and after a latency of 2 days, he developed fatigue, pruritus, and loss of appetite along with abnormal liver tests (with the same biochemical profile as previously), consistent with a positive rechallenge. We believe, through the use of the Roussel-Uclaf Causality Assessment Method and expert opinion, that this is a highly likely or definite example of kratom-induced DILI. With the gaining popularity of this drug, it appears that DILI may be an important complication of kratom for providers to recognize.

CYP450-Mediated Metabolism of Mitragynine and Investigation of Metabolites in Human Urine

Mitragyna speciosa (Kratom) has emerged as a recreational drug and a substance of medicinal intrigue. Although the drug was initially used recreationally for its sedating and euphoric effects, more recently its use has been associated with the non-medically supervised treatment of opioid abstinence syndrome. Mitragynine is the principal pharmacologically active alkaloid in kratom. Although metabolites of mitragynine have been identified, the cytochrome P450 (CYP450) enzymes responsible for its biotransformation are still under investigation. The goal of this study was to contribute further knowledge regarding CYP450 activity as it relates to mitragynine. Recombinant cytochrome P450 enzymes (rCYPs) were used to investigate the isoforms involved in its metabolism. Biotransformational products were identified using liquid chromatography-quadrupole/time of flight-mass spectrometry. Four rCYP enzymes (2C18, 2C19, 2D6 and 3A4) were found to contribute to the metabolism of mitragynine. 7-Hydroxymitragynine (which has an affinity for the mu-opioid receptor &gt;10-folds that of morphine) was produced exclusively by 3A4. 9-O-demethylmitragynine, the most abundant metabolite in vitro (and the most prevalent metabolite in urine among kratom users) was produced by 2C19, 3A4 and 2D6. 16-Carboxymitragynine was produced by rCYPs 2D6, 2C19 and 2C18. 2C19 was solely responsible for the formation of 9-O-demethyl-16-carboxymitragynine. In vitro rCYP studies were compared with phase I metabolites in urine from cases involving mitragynine.

Exploration of cytochrome P450 inhibition mediated drug-drug interaction potential of kratom alkaloids

In vitro cytochrome P450 inhibition of major kratom alkaloids: mitragynine (MTG), speciogynine (SPG), speciocilliatine (SPC), corynantheidine (COR), 7-hydroxymitragynine (7HMG) and paynantheine (PAY) was evaluated using human liver microsomes (HLMs) to understand their drug-drug interaction potential. CYP450 isoform-specific substrates of CYP1A2, 2C8, 2C9, 2C19, 2D6, and 3A4/5 were incubated in HLMs with or without alkaloids. Preliminary CYP450 inhibition (IC50) data were generated for each of these isoforms. In addition, the type of inhibition and estimation of the inhibition constants (Ki) of MTG and COR were determined. Among the tested alkaloids, MTG and COR were potent inhibitors of CYP2D6 (IC50, 2.2 and 4.2 μM, respectively). Both MTG and COR exhibited competitive inhibition of CYP2D6 activity and the Ki were found to be 1.1 and 2.8 μM, respectively. SPG and PAY showed moderate inhibition of CYP2D6 activity. Additionally, moderate inhibitory effects by SPC, MTG, and SPG were observed on CYP2C19 activity. Interestingly, inhibition of only midazolam hydroxylase CYP3A4/5 activity by COR, PAY, and MTG was observed while no inhibitory effect was observed when testosterone was used as a probe substrate. In conclusion, MTG and COR may lead to clinically significant adverse drug interactions upon coadministration of drugs that are substantially metabolized by CYP2D6.

Mitragynine, an euphoric compound inhibits hERG1a/1b channel current and upregulates the complexation of hERG1a-Hsp90 in HEK293-hERG1a/1b cells

Mitragyna speciosa Korth (M. speciosa) has been widely used as a recreational product, however, there are growing concerns on the abuse potentials and toxicity of the plant. Several poisoning and fatal cases involving kratom and mitragynine have been reported but the underlying causes remain unclear. The human ether-a-go-go-related gene 1 (hERG1) encodes the pore-forming subunit underlying cardiac rapidly delayed rectifier potassium current (I_Kr). Pharmacological blockade of the I_Kr can cause acquired long QT syndrome, leading to lethal cardiac arrhythmias. This study aims to elucidate the mechanisms of mitragynine-induced inhibition on hERG1a/1b current. Electrophysiology experiments were carried out using Port-a-Patch system. Quantitative RT-PCR, Western blot analysis, immunofluorescence and co-immunoprecipitation methods were used to determine the effects of mitragynine on hERG1a/1b expression and hERG1-cytosolic chaperones interaction. Mitragynine was found to inhibit the I_Kr current with an IC₅₀ value of 332.70 nM. It causes a significant reduction of the fully-glycosylated (fg) hERG1a protein expression but upregulates both core-glycosylated (cg) expression and hERG1a-Hsp90 complexes, suggesting possible impaired hERG1a trafficking. In conclusion, mitragynine inhibits hERG1a/1b current through direct channel blockade at lower concentration, but at higher concentration, it upregulates the complexation of hERG1a-Hsp90 which may be inhibitory towards channel trafficking.

Characteristics of deaths associated with kratom use

BACKGROUND

Kratom (Mitragyna speciosa Korth) use has increased in Western countries, with a rising number of associated deaths. There is growing debate about the involvement of kratom in these events.

AIMS

This study details the characteristics of such fatalities and provides a 'state-of-the-art' review.

METHODS

UK cases were identified from mortality registers by searching with the terms 'kratom', 'mitragynine', etc. Databases and online media were searched using these terms and 'death', 'fatal*', 'overdose', 'poisoning', etc. to identify additional cases; details were obtained from relevant officials. Case characteristics were extracted into an Excel spreadsheet, and analysed employing descriptive statistics and thematic analysis.

RESULTS

Typical case characteristics (n = 156): male (80%), mean age 32.3 years, White (100%), drug abuse history (95%); reasons for use included self-medication, recreation, relaxation, bodybuilding, and avoiding positive drug tests. Mitragynine alone was identified/implicated in 23% of cases. Poly substance use was common (87%), typically controlled/recreational drugs, therapeutic drugs, and alcohol. Death cause(s) included toxic effects of kratom ± other substances; underlying health issues.

CONCLUSIONS

These findings add substantially to the knowledge base on kratom-associated deaths; these need systematic, accurate recording. Kratom's safety profile remains only partially understood; toxic and fatal levels require quantification.

Kratom policy: The challenge of balancing therapeutic potential with public safety

Kratom (Mitragyna speciosa) is a tree-like plant indigenous to Southeast Asia. Its leaves, and the teas brewed from them have long been used by people in that region to stave off fatigue and to manage pain and opioid withdrawal. Evidence suggests kratom is being increasingly used by people in the United States and Europe for the self-management of opioid withdrawal and treatment of pain. Recent studies have confirmed that kratom and its chemical constituents have potentially useful pharmacological actions. However, there have also been increasing numbers of reports of adverse effects resulting from use of kratom products. In August 2016, the US Drug Enforcement Administration announced plans to classify kratom and its mitragynine constituents as Schedule I Controlled Substances, a move that triggered a massive response from pro-kratom advocates. The debate regarding the risks, and benefits and safety of kratom continues to intensify. Kratom proponents tout kratom as a safer and less addictive alternative to opioids for the management of pain and opioid addiction. The anti-kratom faction argues that kratom, itself, is a dangerous and addictive drug that ought to be banned. Given the widespread use of kratom and the extensive media attention it is receiving, it is important for physicians, scientists and policy makers to be knowledgeable about the subject. The purpose of this commentary is to update readers about recent developments and controversies in this rapidly evolving area. All of the authors are engaged in various aspects of kratom research and it is our intention to provide a fair and balanced overview that can form the basis for informed decisions on kratom policy. Our conclusions from these analyses are: (a) User reports and results of preclinical studies in animals strongly suggest that kratom and its main constituent alkaloid, mitragynine may have useful activity in alleviating pain and managing symptoms of opioid withdrawal, even though well-controlled clinical trials have yet to be done. (b) Even though kratom lacks many of the toxicities of classic opioids, there are legitimate concerns about the safety and lack of quality control of purported "kratom" products that are being sold in the US. (c) The issues regarding the safety and efficacy of kratom and its mitragynine constituent can only be resolved by additional research. Classification of the Mitragyna alkaloids as Schedule I controlled substances would substantially impede this important research on kratom.

Current perspectives on the impact of Kratom use

The leaves from the tree Mitragyna speciosa, commonly known as Kratom, in the coffee plant family (Rubiaceae) are commonly used in their native habitat of Southeast Asia as a stimulant to sustain energy during hard day labor and as an opioid-like analgesic and sedative. Traditional and modern uses overlap based on the effects of the leaf extract which has also gained popularity in the United States and Europe in the last two decades. Kratom has and is being used for the mitigation of opioid withdrawal symptoms and as a harm reduction agent with a minority of users subsequently developing a dependence on the extract. The respective demographic use patterns of Kratom differ between Southeast Asia and the Western world. While pure Kratom is primarily used by day laborers and misused in conjunction with cough medicine by youth in Southeast Asia, a majority of users in the United States is middle-aged, has at least middle income, private health insurance, and completed some college. Deaths attributed to the use of Kratom have been reported in Europe and the United States but not in Southeast Asia. Although Kratom was detected as the alkaloid mitragynine in the blood of the decedents, causality could not be established in almost all cases because of poly-drug exposures. It is notable that Kratom can cause herb–drug interactions, especially with other central nervous system -active substances. Given the mostly unregulated market for Kratom products in Western countries, consumers may be exposed to adulterated or contaminated products, especially if purchased through websites or the darknet. A number of countries have scheduled Kratom because of its stimulant- and opioid-like effects and the established interaction of the alkaloid mitragynine with opioid receptors.

Pharmacokinetics of mitragynine, a major analgesic alkaloid in kratom (Mitragyna speciosa): A systematic review

BACKGROUND AND OBJECTIVE

Kratom (Mitragyna speciosa) is a tropical tree found in southern Thailand and northern states of the Malay Peninsula. Kratom is commercially available and used as an alternative to treat opioid withdrawal. Mitragynine is the major indole alkaloid found in kratom leaves. This review aimed to summarize available pharmacokinetic information about mitragynine.

METHODS

PubMed, Scopus, and Web of Science were systematically searched from their inceptions to June 2018. All types of pharmacokinetic studies of mitragynine were included for further systematic review.

RESULTS

Seventeen articles were reviewed. Mitragynine is a lipophilic weak base passively transported across the intestinal wall and blood brain barrier. 85-95% is bound to plasma protein and extensively metabolized by phase I and particularly phase II enzymes. Actions on CYP enzymes are unlikely to impact drug metabolism at concentrations likely to exist in kratom-consuming humans. In rats and humans, mitragynine is rapidly absorbed after orally administration (T_max˜1.5 h, C_max˜0.3-1.8 μM). V_d was 37-90 L/kg; t_1/2 was 3-9 hr; mostly excreted as metabolites in urine. Bioavailability was estimated as 21%. It also rapidly penetrated and redistributed in brain. A quality assessment tool tailored for pharmacokinetic studies was also created which rated some studies of lower value.

CONCLUSION

Rudimentary pharmacokinetics of mitragynine was described in this systematic review. However, the discovered studies provided scant information on the role of metabolism and redistribution into tissues nor the rate of excretion.

Intestinal permeability of mitragynine in rats using in situ absorption model

The intestinal permeability of mitragynine was investigated in situ using a single pass intestinal perfusion (SPIP) absorption model, in small intestine of rat using mitragynine in the absence/presence of the permeability markers, P-gp and/or CYP3A4 inhibitors. Mitragynine demonstrated high intestinal permeability (P_eff of 1.11 × 10^-4 cm/s) that is in the range of highly permeable drugs such as propranolol (P_eff of 1.27 × 10^-4 cm/s) indicating that it readily crosses the intestine. The addition of azithromycin (P-glycoprotein inhibitor) and ciprofloxacin (CYP3A4 inhibitor) or combination of both has no effect on intestinal permeability of mitragynine across the rat small intestine.

Mitragyna speciosa: Clinical, Toxicological Aspects and Analysis in Biological and Non-Biological Samples

The abuse of psychotropic substances is a well-known phenomenon, and many of them are usually associated with ancestral traditions and home remedies. This is the case of Mitragyna speciosa (kratom), a tropical tree used to improve work performance and to withstand great heat. According to several published studies, the main reasons for kratom consumption involve improving sexual performance and endurance, but also social and recreational uses for the feeling of happiness and euphoria; it is also used for medical purposes as a pain reliever, and in the treatment of diarrhea, fever, diabetes, and hypertension. However, this plant has gained more popularity amongst young people over the last years. Since it is available on the internet for purchase, its use is now widely as a drug of abuse, namely as a new psychoactive substance, being a cheaper alternative to opioids that does not require medical prescription in most countries. According to internet surveys by the European Monitoring Centre for Drugs and Drug Addiction in 2008 and 2011, kratom was one of the most widely supplied new psychoactive substances. The composition of kratom is complex; in fact, more than 40 different alkaloids have been identified in Mitragyna speciosa so far, the major constituent being mitragynine, which is exclusive to this plant. Besides mitragynine, alkaloids such as corynantheidine and 7-hydroxamitragynine also present pharmacological effects, a feature that may be attributed to the remaining constituents as well. The main goal of this review is not only to understand the origin, chemistry, consumption, and analytical methodologies for analysis and mechanism of action, but also the use of secondary metabolites of kratom as therapeutic drugs and the assessment of potential risks associated with its consumption, in order to aid health professionals, toxicologists, and police authorities in cases where this plant is present.

Fatal combination of mitragynine and quetiapine - a case report with discussion of a potential herb-drug interaction

Kratom is a plant with dose-dependent mixed stimulant and opioid properties whose pharmacologic characteristics and social impact continue to be described. The main active isolate of kratom is mitragynine, an indole-containing alkaloid with opioid-like effects. Kratom toxicity and kratom-associated fatalities have been described, including those in association with additional drugs. In this paper we describe the case of a 27-year-old man who was found deceased with a toxic blood concentration of quetiapine in conjunction with the qualitative presence of mitragynine. Investigative and autopsy findings suggested perimortem hyperthermia and seizure-like activity. Kratom toxicity and kratom-associated fatalities are being increasingly reported. Experiments with kratom extracts have shown inhibitory effects upon hepatic CYP enzymes, leading to previous speculation of the potential for clinically significant interactions between kratom and a wide array of medications. Herein is described a fatal case of quetiapine toxicity complicated by mitragynine use. The potential ability of mitragynine to alter the pharmacokinetics of a prescription medication via inhibition of its hepatic metabolism is discussed.

Evaluating the hematological and clinical-chemistry parameters of kratom (Mitragyna speciosa) users in Malaysia

ETHNOPHARMACOLOGICAL RELEVANCE

Kratom (Mitragyna speciosa Korth.) from the Rubiaceae family is an indigenous tropical medicinal tree of Southeast Asia. Kratom leaves have been used for decades in Malaysia and Thailand in traditional context for its perceived vast medicinal value, and as a mild stimulant among manual labourers. Kratom consumption has been reported to cause side-effects in kratom users.

AIM OF THE STUDY

To evaluate kratom's effects towards hematological and clinical-chemistry parameters among regular kratom users in Malaysia.

METHODS

A total of 77 subjects (n=58 regular kratom users, and n=19 healthy controls) participated in this cross-sectional study. All the surveys were conducted through face-to-face interview to elicit subject's socio-demographic characteristics and kratom use history. A full-blood test was also administered. Laboratory analysis was conducted using GC-MS to determine mitragynine content in the acquired kratom samples in order to relate mitragynine consumption with possible alterations in the blood parameters of kratom users.

RESULTS

Findings showed that there were no significant differences in the hematological and clinical-chemistry parameters of traditional kratom users and healthy controls, except for HDL and LDL cholesterol values; these were found to be above the normal reference range for the former. Similarly, long-term kratom consumption (>5 years), and quantity of daily kratom use (≥3 ½ glasses; mitragynine content 76.3-114.8mg) did not appear to alter the hematological and biochemical parameters of kratom users.

CONCLUSION

These data suggest that even long-term and heavy kratom consumption did not significantly alter the hematological and clinical-chemistry parameters of kratom users in a traditional setting.

Neurobiology of Kratom and its main alkaloid mitragynine

Kratom or its main alkaloid, mitragynine is derived from the plant Mitragyna speciosa Korth which is indigenous to Southeast Asian countries. This substance has become widely available in other countries like Europe and United States due to its opium- and coca-like effects. In this article, we have reviewed available reports on mitragynine and other M. speciosa extracts. M. speciosa has been proven to have a rewarding effect and is effective in alleviating the morphine and ethanol withdrawal effects. However, studies in human revealed that prolonged consumption of this plant led to dependence and tolerance while cessation caused a series of aversive withdrawal symptoms. Findings also showed that M. speciosa extracts possess antinociceptive, anti-inflammatory, anti-depressant, and muscle relaxant properties. Available evidence further supports the adverse effects of M. speciosa preparations, mitragynine on cognition. Pharmacological activities are mainly mediated via opioid receptors as well as neuronal Ca²⁺ channels, expression of cAMP and CREB protein and via descending monoaminergic system. Physicochemical properties of mitragynine have been documented which may further explain the variation in pharmacological responses. In summary, current researchs on its main indole alkaloid, mitragynine suggest both therapeutic and addictive potential but further research on its molecular effects is needed.

Upregulation of microRNA-375 increases the cisplatin-sensitivity of human gastric cancer cells by regulating ERBB2

Resistance to chemotherapy is a major challenge in the effective treatment of patients with gastric cancer; however, the mechanisms underlying chemoresistance in gastric cancer cells are yet to be elucidated. MicroRNAs (miRNAs) have previously been associated with cancer progression and sensitivity to chemotherapy; therefore, the present study aimed to identify miRNAs that may influence the sensitivity of human gastric cancer cells to cisplatin (DDP) treatment. Initially, miRNAs that were differentially expressed between the DDP-sensitive SGC7901 human gastric cancer cell line and DDP-resistant SGC7901/DDP cell line were identified using high-throughput sequencing technology. miRNA-375 (miR-375), which was shown to be downregulated in the SGC7901/DDP cells, has previously been associated with numerous types of cancer; however, to the best of our knowledge, a role for miR-375 in the DDP-sensitivity of gastric cancer cells has yet to be explored. In the present study, the expression levels of miR-375 were significantly downregulated in the SGC7901/DDP cells, as compared with the SGC7901 cells, as demonstrated by reverse transcription-quantitative polymerase chain reaction. In addition, upregulation of miR-375 significantly enhanced the anti-proliferative and apoptosis-inducing effects of DDP, whereas downregulation of miR-375 decreased these effects. Subsequently, western blot analysis demonstrated that upregulation of miR-375 in the SGC7901/DDP cells increased their sensitivity to DDP treatment via regulating the protein expression levels of erb-b2 receptor tyrosine kinase 2 and phosphorylated-Akt. The results of the present study indicate that the expression levels of miR-375 may influence the sensitivity of human gastric cancer cells to the effects of DDP; thus suggesting that a combination of miR-375 regulation and DDP may be considered a novel strategy in the treatment of patients with chemoresistant gastric cancer.

ZHX2 enhances the cytotoxicity of chemotherapeutic drugs in liver tumor cells by repressing MDR1 via interfering with NF-YA

We previously reported the tumor suppressor function of Zinc-fingers and homeoboxes 2 (ZHX2) in hepatocellular carcinoma (HCC). Other studies indicate the association of increased ZHX2 expression with improved response to high dose chemotherapy in multiple myeloma. Here, we aim to test whether increased ZHX2 levels in HCC cells repress multidrug resistance 1(MDR1) expression resulting in increased sensitivity to chemotherapeutic drugs. We showed evidence that increased ZHX2 levels correlated with reduced MDR1 expression and enhanced the cytotoxicity of CDDP and ADM in different HCC cell lines. Consistently, elevated ZHX2 significantly reduced ADM efflux in HepG2 cells and greatly increased the CDDP-mediated suppression of liver tumor growth in vivo. Furthermore, immunohistochemical staining demonstrated the inverse correlation of ZHX2 and MDR1 expression in HCC tissues. Luciferase report assay showed that ZHX2 repressed the MDR1 promoter activity, while knockdown of NF-YA or mutating the NF-Y binding site eliminated this ZHX2-mediated repression of MDR1 transcription. Co-IP and ChIP assay further suggested that ZHX2 interacted with NF-YA and reduced NF-Y binding to the MDR1 promoter. Taken together, we clarify that ZHX2 represses NF-Y-mediated activation of MDR1 transcription and, in doing so, enhances the effects of chemotherapeutics in HCC cells both in vitro and in vivo.

Following "the Roots" of Kratom (Mitragyna speciosa): The Evolution of an Enhancer from a Traditional Use to Increase Work and Productivity in Southeast Asia to a Recreational Psychoactive Drug in Western Countries

The use of substances to enhance human abilities is a constant and cross-cultural feature in the evolution of humanity. Although much has changed over time, the availability on the Internet, often supported by misleading marketing strategies, has made their use even more likely and risky. This paper will explore the case of Mitragyna speciosa Korth. (kratom), a tropical tree used traditionally to combat fatigue and improve work productivity among farm populations in Southeast Asia, which has recently become popular as novel psychoactive substance in Western countries. Specifically, it (i) reviews the state of the art on kratom pharmacology and identification; (ii) provides a comprehensive overview of kratom use cross-culturally; (iii) explores the subjective experiences of users; (iv) identifies potential risks and side-effects related to its consumption. Finally, it concludes that the use of kratom is not negligible, especially for self-medication, and more clinical, pharmacological, and socioanthropological studies as well as a better international collaboration are needed to tackle this marginally explored phenomenon.

Effects of Mitragynine and a Crude Alkaloid Extract Derived from Mitragyna speciosa Korth. on Permethrin Elimination in Rats

Detoxification and elimination of permethrin (PM) are mediated by hydrolysis via carboxylesterase (CES). Mitragyna speciosa (kratom) contains mitragynine (MG) and other bioactive alkaloids. Since PM and MG have the same catalytic site and M. speciosa is usually abused by adding other ingredients such as pyrethroid insecticides, the effects of MG and an alkaloid extract (AE) on the elimination of PM were investigated in rats. Rats were subjected to single and multiple pretreatment with MG and AE prior to receiving a single oral dose (460 mg/kg) of PM. Plasma concentrations of trans-PM and its metabolite phenoxybenzylalcohol (PBAlc) were measured. The elimination rate constant (k_el) and the elimination half-life (t_{1/2 el}) of PM were determined, as well as the metabolic ratio (PMR).A single and multiple oral pretreatment with MG and AE altered the plasma concentration-time courses of both trans-PM and PBAlc during 8–22 h, decreased the PMRs, delayed elimination of PM, but enhanced elimination of PBAlc. Results indicated that PM–MG or AE toxicokinetic interactions might have resulted from the MG and AE interfering with PM hydrolysis. The results obtained in rats suggest that in humans using kratom cocktails containing PM, there might be an increased risk of PM toxicity due to inhibition of PM metabolism and elimination.