Abuse liability of mitragynine assessed with a self-administration procedure in rats

Acute mitragynine administration suppresses cortical oscillatory power and systems theta coherence in rats

BACKGROUND

Mitragynine is the major alkaloid of Mitragyna speciosa (kratom) with potential as a therapeutic in pain management and in depression. There has been debate over the potential side effects of the drug including addiction risk and cognitive decline.

AIMS

To evaluate the effects of mitragynine on neurophysiological systems function in the prefrontal cortex (PFC), cingulate cortex (Cg), orbitofrontal cortex, nucleus accumbens (NAc), hippocampus (HIP), thalamus (THAL), basolateral amygdala (BLA) and ventral tegmental area of rats.

METHODS

Local field potential recordings were taken from animals at baseline and for 45 min following mitragynine administration (10 mg/kg, intraperitoneally). Drug-induced changes in spectral power and coherence between regions at specific frequencies were evaluated. Mitragynine-induced changes in c-fos expression were also analyzed.

RESULTS

Mitragynine increased delta power and reduced theta power in all three cortical regions that were accompanied by increased c-fos expression. A transient suppression of gamma power in PFC and Cg was also evident. There were no effects of mitragynine on spectral power in any of the other regions. Mitragynine induced a widespread reduction in theta coherence (7-9 Hz) that involved disruptions in cortical and NAc connectivity with the BLA, HIP and THAL.

CONCLUSIONS

These findings show that mitragynine induces frequency-specific changes in cortical neural oscillatory activity that could potentially impact cognitive functioning. However, the absence of drug effects within regions of the mesolimbic pathway may suggest either a lack of addiction potential, or an underlying mechanism of addiction that is distinct from other opioid analgesic agents.

Mitragynine, bioactive alkaloid of kratom, reduces chemotherapy-induced neuropathic pain in rats through α-adrenoceptor mechanism

BACKGROUND AND PURPOSE

Kratom is a coffee-like plant containing compounds that cause opioid and stimulant effects. The most prevalent bioactive alkaloid of kratom is mitragynine (MG). Opioid effects of MG are apparent (e.g. antinociception and nanomolar affinity for μ, κ and δ opioid receptors), but effects encompassing interactions with additional systems, such as adrenergic and dopaminergic, remain undefined. Given that enhanced adrenergic transmission is a mechanism common to most first-line neuropathic pain medications, we tested the hypothesis that MG reduces chemotherapy-induced neuropathic pain through a mechanism involving α-adrenoceptor activation.

METHODS

Rats were injected once with oxaliplatin (6 mg/kg IP) to induce allodynia and then treated with MG (0, 1, 5, 10 mg/kg IP) for 5-7 days. To investigate receptor mechanisms, a fixed dose of MG (5 mg/kg IP) was injected with yohimbine (5 mg/kg IP, α₂-adrenoceptor antagonist), prazosin (5 mg/kg IP, α₁-adrenoceptor antagonist), or naltrexone (5 mg/kg IP, opioid antagonist).

KEY RESULTS

MG (5, 10 mg/kg) dose-dependently reduced mechanical sensitivity in oxaliplatin-injected rats. Anti-allodynic effects of MG were completely inhibited by yohimbine, and significantly reduced by prazosin and naltrexone. MG produced modest hyperlocomotion but only at a dose (30 mg/kg) higher than those required to reduce allodynia.

CONCLUSION AND IMPLICATION

The finding that MG reduced neuropathic pain through a mechanism requiring active α-adrenoceptors indicates that the pharmacological profile of MG includes activation of adrenergic, as well as opioid, systems.

Evaluating kratom alkaloids using PHASE

Kratom is a botanical substance that is marketed and promoted in the US for pharmaceutical opioid indications despite having no US Food and Drug Administration approved uses. Kratom contains over forty alkaloids including two partial agonists at the mu opioid receptor, mitragynine and 7-hydroxymitragynine, that have been subjected to the FDA's scientific and medical evaluation. However, pharmacological and toxicological data for the remaining alkaloids are limited. Therefore, we applied the Public Health Assessment via Structural Evaluation (PHASE) protocol to generate in silico binding profiles for 25 kratom alkaloids to facilitate the risk evaluation of kratom. PHASE demonstrates that kratom alkaloids share structural features with controlled opioids, indicates that several alkaloids bind to the opioid, adrenergic, and serotonin receptors, and suggests that mitragynine and 7-hydroxymitragynine are the strongest binders at the mu opioid receptor. Subsequently, the in silico binding profiles of a subset of the alkaloids were experimentally verified at the opioid, adrenergic, and serotonin receptors using radioligand binding assays. The verified binding profiles demonstrate the ability of PHASE to identify potential safety signals and provide a tool for prioritizing experimental evaluation of high-risk compounds.

Kratom (Mitragyna speciosa): User demographics, use patterns, and implications for the opioid epidemic

BACKGROUND

Kratom, a Southeast Asian plant with opioid-receptor mediated effects, has emerged as a potential substance of abuse, with limited data on its use and effects. This study characterized kratom user demographics, use patterns, and perceived drug effects.

METHODS

A cross-sectional, anonymous online survey was conducted between January and December 2017.

RESULTS

2,798 kratom users - mean age 40 (SD = 12); predominantly White (90 %), female (61 %), and located in the US (97 %) - completed the survey. Kratom was primarily taken orally in doses of 1-3 g (49 %), with daily use (59 %) being most common. Kratom was used for pain (91 %), anxiety (67 %), and depression (65 %), with high ratings of effectiveness. 1,144 (41 %) used kratom to stop or reduce prescription or illicit opioid use, citing decreased opioid withdrawal and craving related to kratom use, with 411 reporting >1-year continuous abstinence from opioids attributed to kratom use. Roughly one-third of respondents reported adverse effects of kratom, largely rated as mild in severity and lasting ≤24 h. Seventeen participants (0.6 %) sought treatment for adverse effects. Fifty-six individuals (2 %) met DSM-5 criteria for a past-year moderate or severe kratom-related substance use disorder (SUD). When asked how troubled they felt regarding their kratom use, the mean (SD) rating was 3.2 (9.8) on a scale from 0 to 100.

CONCLUSION

Kratom is used among White, middle-aged Americans for symptoms of pain, anxiety, depression, and opioid withdrawal. Although regular use was typical, kratom-related SUD and serious adverse effects were uncommon. Additional research on kratom epidemiology and pharmacology is imperative in light of the present opioid epidemic.

Patterns and reasons for kratom (Mitragyna speciosa) use among current and former opioid poly-drug users

ETHNOPHARMACOLOGICAL RELEVANCE

Kratom (Mitragyna speciosa) is a native medicinal plant of Southeast Asia widely reported to be used to reduce opioid dependence and mitigate withdrawal symptoms. There is also evidence to suggest that opioid poly-drug users were using kratom to abstain from opioids.

AIM OF THE STUDY

To determine the patterns and reasons for kratom use among current and former opioid poly-drug users in Malaysia.

MATERIALS AND METHODS

A total of 204 opioid poly-drug users (142 current users vs. 62 former users) with current kratom use history were enrolled into this cross-sectional study. A validated UPLC-MS/MS method was used to evaluate the alkaloid content of a kratom street sample.

RESULTS

Results from Chi-square analysis showed that there were no significant differences in demographic characteristics between current and former opioid poly-drug users except with respect to marital status. Current users had higher odds of being single (OR: 2.2: 95%CI: 1.21-4.11; p < 0.009). Similarly, there were no significant differences in the duration (OR: 1.1: 0.62-2.03; p < 0.708), daily quantity (OR: 1.5: 0.85-2.82; p < 0.154) or frequency of kratom use between current and former opioid poly-drug users (OR: 1.1: 0.62-2.06; p < 0.680). While both current and former opioid users reported using kratom to ameliorate opioid withdrawal, current users had significantly higher likelihood of using kratom for that purpose (OR: 5.4: 95%CI: 2.81-10.18; p < 0.0001). In contrast, former opioid users were more likely to be using kratom for its euphoric (mood elevating) effects (OR: 1.9: 95%CI: 1.04-3.50; p < 0.035). Results from the UPLC-MS/MS analysis indicated the major alkaloids present in the representative kratom street sample (of approximately 300 mL of brewed kratom) were mitragynine, followed by paynantheine, speciociliatine and speciogynine, as well as low levels of 7-hydroxymitragynine.

CONCLUSIONS

Both current and former opioid poly-drug users regularly used kratom (three glasses or about 900 mL daily or the equivalent of 170.19 mg of mitragynine) to overcome opioid poly-drug use problems.

Assessing physiological dependence and withdrawal potential of mitragynine using schedule-controlled behaviour in rats

RATIONALE

Kratom is proposed to exhibit therapeutic potential as an opium substitute, but little is known about its dependence-producing profile, particularly of its main psychoactive compound, mitragynine (MG).

OBJECTIVES

This study examined the dependence-producing effects of MG using operant-scheduled behaviour in rats and investigated the potential therapeutic effect of MG by comparing effects to buprenorphine in morphine-dependent rats using the same schedule-controlled behavioural task.

METHODS

The effects of acutely administered MG and morphine were determined in rats trained to respond under fixed-ratio (FR) 10 schedule of food reinforcement. Next, the rats were administered MG and morphine twice daily for 14 consecutive days to determine if physiological dependence would develop by examining cessation of drug treatment and following antagonist-precipitated withdrawal. The study then examined the effects of MG substitution to suppress naloxone-precipitated morphine withdrawal effects on scheduled responding.

RESULTS

Acute doses of MG did not produce dose-related decreases on FR schedules of responding compared to morphine. Unlike morphine, MG-treated rats showed no suppression of response rates following cessation of MG treatment. However, withdrawal effects were evident for MG after precipitation by either naloxone or SR141716A (rimonabant), similar to morphine-treated rats. MG in higher doses (10 and 30 mg/kg) attenuated the naloxone-precipitated morphine withdrawal effects while smaller doses of buprenorphine (0.3 and 1.0 mg/kg) were necessary to alleviate these effects.

CONCLUSION

The findings suggest that MG does not induce physiological dependence but can alleviate the physical symptoms associated with morphine withdrawal which represent the desired characteristics of novel pharmacotherapeutic interventions for managing opioid use disorder (OUD).

Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom Alkaloids

Selected indole-based kratom alkaloids were evaluated for their opioid and adrenergic receptor binding and functional effects, in vivo antinociceptive effects, plasma protein binding, and metabolic stability. Mitragynine, the major alkaloid in Mitragyna speciosa (kratom), had higher affinity at opioid receptors than at adrenergic receptors while the vice versa was observed for corynantheidine. The observed polypharmacology of kratom alkaloids may support its utilization to treat opioid use disorder and withdrawal.

Self-Report Data on Regular Consumption of Illicit Drugs and HIV Risk Behaviors after Kratom (Mitragyna Speciosa korth.) Initiation among Illicit Drug Users in Malaysia

This study sought to determine the relationship between kratom (Mitragyna speciosa) initiation and regular consumption of illicit drugs and HIV risk behaviors in a cohort of illicit drug users in Malaysia. 260 illicit drug users with current kratom use were recruited through convenience sampling for this cross-sectional study. All were male, with the majority being Malays (95%, n = 246/260). Results suggest that kratom initiation was associated with significant decrease in the regular use of heroin (odds ratio (OR) = 0.50, 95% confidence interval (CI): 0.40- 0.72; p = .0001), methamphetamine (OR = 0.23, CI: 0.16- 0.35; p < .0001), and amphetamine (OR = 0.17, CI: 0.09- 0.34; p < .0001). Kratom initiation was also associated with reduction in regular HIV risk behaviors such as having sex with sex workers (OR = 0.20, CI: 0.12-0.32; p < .0001), using drugs before sexual intercourse (OR = 0.20, CI: 0.13- 0.31; p < .0001), injecting behaviors (OR = 0.10, CI: 0.04- 0.25; p < .0001), sharing of injection equipment (OR = 0.13, CI: 0.04- 0.43; p < .0001), and injecting with other injection drug users (IDUs) (OR = 0.07, CI: 0.02- 0.24; p < .0001).

Kratom as a substitute for opioids: Results from an online survey

BACKGROUND

Kratom is a South Eastern Asian tree whose leaves are used to make tea-like brews or swallowed in powdered form for various health and well-being reasons including to relieve pain and opioid withdrawal. It is important to learn more about the potential public health impact of kratom in the context of the opioid epidemic.

METHODS

An anonymous online survey of kratom users (2867 current users and 157 former users) was conducted in September 2017 through the American Kratom Association and associated social media sites.

RESULTS

Kratom was used primarily to relieve pain (endorsed by 48% of respondents), for anxiety, PTSD, or depression (22%), to increase energy or focus (10%) and to help cut down on opioid use and/or relieve withdrawal (10%). Over 90% of respondents who used it in place of opioids indicated that it was helpful to relieve pain, reduce opioid use, and relieve withdrawal. The reported incidence of bad adverse reactions was 13%, and reactions were overwhelmingly mild and self-managed.

CONCLUSIONS

Respondents reported using kratom for conditions which often require use of opioids, including pain and reduction of opioid use. The high self-reported efficacy and low incidence of adverse reactions associated with kratom use suggest that it may provide a potential alternative to opioids for some persons even though it has not been evaluated in multi-center clinical trials or approved for any therapeutic purpose. Further study of kratom, including systematic characterization of its safety and efficacy for various conditions is warranted.

The effects of mitragynine and morphine on schedule-controlled responding and antinociception in rats

RATIONALE

Mitragyna speciosa (kratom) may hold promise as both an analgesic and treatment for opioid use disorder. Mitragynine, its primary alkaloid constituent, is an opioid receptor ligand. However, the extent to which the in vivo effects of mitragynine are mediated by opioid receptors, or whether mitragynine interacts with other opioid agonists, is not fully established.

OBJECTIVES

The effects of mitragynine and the prototypical opioid agonist morphine were compared for their capacity to decrease operant responding for food delivery, and to increase response latency to a thermal stimulus.

METHODS

Male and female Sprague-Dawley rats responded under a multiple cycle fixed ratio 10 schedule of food delivery and were tested on a hot plate (52 °C) immediately after each cycle. Morphine and mitragynine were administered alone, in combination with each other, and in combination with the opioid antagonist naltrexone.

RESULTS

Morphine and mitragynine dose-dependently decreased schedule-controlled responding; the ED50 values were 7.3 and 31.5 mg/kg, respectively. Both drugs increased thermal antinociception; the ED50 value for morphine was 18.3. Further, doses of naltrexone that antagonized morphine did not antagonize mitragynine. Mitragynine (17.8 mg/kg) did not alter the rate-decreasing or antinociceptive effects of morphine.

CONCLUSIONS

The antinociceptive effects of mitragynine and morphine occur at doses larger than those that disrupt learned behavior. Opioid receptors do not appear to mediate the disruptive effects of mitragynine on learned behavior. Mitragynine had lesser antinociceptive effects than morphine, and these did not appear to be mediated by opioid receptors. The pharmacology of mitragynine includes a substantial non-opioid mechanism.

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.

7-Hydroxymitragynine Is an Active Metabolite of Mitragynine and a Key Mediator of Its Analgesic Effects

Mitragyna speciosa, more commonly known as kratom, is a plant native to Southeast Asia, the leaves of which have been used traditionally as a stimulant, analgesic, and treatment for opioid addiction. Recently, growing use of the plant in the United States and concerns that kratom represents an uncontrolled drug with potential abuse liability, have highlighted the need for more careful study of its pharmacological activity. The major active alkaloid found in kratom, mitragynine, has been reported to have opioid agonist and analgesic activity in vitro and in animal models, consistent with the purported effects of kratom leaf in humans. However, preliminary research has provided some evidence that mitragynine and related compounds may act as atypical opioid agonists, inducing therapeutic effects such as analgesia, while limiting the negative side effects typical of classical opioids. Here we report evidence that an active metabolite plays an important role in mediating the analgesic effects of mitragynine. We find that mitragynine is converted in vitro in both mouse and human liver preparations to the much more potent mu-opioid receptor agonist 7-hydroxymitragynine and that this conversion is mediated by cytochrome P450 3A isoforms. Further, we show that 7-hydroxymitragynine is formed from mitragynine in mice and that brain concentrations of this metabolite are sufficient to explain most or all of the opioid-receptor-mediated analgesic activity of mitragynine. At the same time, mitragynine is found in the brains of mice at very high concentrations relative to its opioid receptor binding affinity, suggesting that it does not directly activate opioid receptors. The results presented here provide a metabolism-dependent mechanism for the analgesic effects of mitragynine and clarify the importance of route of administration for determining the activity of this compound. Further, they raise important questions about the interpretation of existing data on mitragynine and highlight critical areas for further research in animals and humans.

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.

Simultaneous quantification of ten key Kratom alkaloids in Mitragyna speciosa leaf extracts and commercial products by ultra-performance liquid chromatography-tandem mass spectrometry

Kratom (Mitragyna speciosa) is a psychoactive plant popular in the United States for the self-treatment of pain and opioid addiction. For standardization and quality control of raw and commercial kratom products, an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the quantification of ten key alkaloids, namely: corynantheidine, corynoxine, corynoxine B, 7-hydroxymitragynine, isocorynantheidine, mitragynine, mitraphylline, paynantheine, speciociliatine, and speciogynine. Chromatographic separation of diastereomers, or alkaloids sharing same ion transitions, was achieved on an Acquity BEH C18 column with a gradient elution using a mobile phase containing acetonitrile and aqueous ammonium acetate buffer (10mM, pH 3.5). The developed method was linear over a concentration range of 1-200 ng/mL for each alkaloid. The total analysis time per sample was 22.5 minutes. The analytical method was validated for accuracy, precision, robustness, and stability. After successful validation, the method was applied for the quantification of kratom alkaloids in alkaloid-rich fractions, ethanolic extracts, lyophilized teas, and commercial products. Mitragynine (0.7%-38.7% w/w), paynantheine (0.3%-12.8% w/w), speciociliatine (0.4%-12.3% w/w), and speciogynine (0.1%-5.3% w/w) were the major alkaloids in the analyzed kratom products/extracts. Minor kratom alkaloids (corynantheidine, corynoxine, corynoxine B, 7-hydroxymitragynine, isocorynantheidine) were also quantified (0.01%-2.8% w/w) in the analyzed products; however mitraphylline was below the lower limit of quantification in all analyses.

Motives for using Kratom (Mitragyna speciosa Korth.) among regular users in Malaysia

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Mitragyna speciosa (Korth.) or kratom have been traditionally used in Malaysia and Thailand mainly to enhance work productivity, as a folk remedy for treating common ailments, and as a mood enhancer.

AIM OF THE STUDY

This present study sought to investigate kratom use motives among regular kratom users in Malaysia.

MATERIALS AND METHODS

A total of 116 regular kratom users were recruited for this cross-sectional survey. The Drinking Motives Questionnaire (DMQ) was administered to measure kratom use motives.

RESULTS

Our results indicate that heavy (>3 glasses daily, each glass contains 48.24-50.4 mg of mitragynine) kratom use was associated with coping (t_87.09 =3.544, p < 0.001), and enhancement (t₁₁₄ =2.180, p = 003). Single subjects had higher mean scores on the coping domain, relative to married subject (t_113.89 =3.029, p < 0.003), while those earning more than RM1500 per month had higher mean scores on the enhancement domain, compare to those earning less than RM1500 per month (t₁₀₇ =2.151, p < 0.034). Higher scores on the coping domain was significantly associated with higher (>3 glasses daily) kratom consumption (p < 0.0045).

CONCLUSIONS

Coping was associated with high (>3 glasses daily) kratom consumption among regular kratom users in traditional, rural settings.