Metabolomics of methadone: clinical and forensic toxicological implications and variability of dose response

Methadone and Buprenorphine in the Perioperative Setting: A Review of the Literature

PURPOSE OF REVIEW

The purpose of this review is to highlight the most recent literature and guidelines regarding perioperative methadone and buprenorphine use.

RECENT FINDINGS

Surgical patients taking methadone and buprenorphine are being encountered more frequently in the perioperative period, and providers are becoming more familiar with their pharmacologic properties, benefits as well as precautions. Recommendations pertaining to buprenorphine therapy in the perioperative settings have changed in recent years, owing to more clinical and basic science research. In addition to their use in chronic pain and opioid use disorders, they can also be initiated for acute postoperative pain indications, in select patients and situations. Methadone and buprenorphine are being more commonly prescribed for pain management and opioid use disorder, and their continuation during the perioperative period is generally recommended, to reduce the risk of opioid withdrawal, relapse, or inadequately controlled pain. Additionally, both may be initiated safely and effectively for acute pain management during and after the operating room period.

Buprenorphine Use for Analgesia in Palliative Care

Buprenorphine is a semi-synthetic long-acting partial µ-opioid receptor (MOR) agonist that can be used for chronic pain as a sublingual tablet, transdermal patch (Butrans®), or a buccal film (Belbuca®). Buprenorphine's unique high receptor binding affinity and slow dissociation at the MOR allow for effective analgesia while offering less adverse effects compared to a full agonist opioid, in particular, less concern for respiratory depression and constipation. It is underused in chronic pain and palliative care due to misconceptions and stigma from its use in opioid use disorder (OUD). This case report discusses the unique pharmacology of buprenorphine, including its advantages, disadvantages, available formulations, drug-drug interactions, initiation and conversion strategies, and identifies ideal populations for use, especially within the palliative care patient population.

A new coaxial flow-through probe for electromembrane extraction of methadone from clinical samples on-line coupled to capillary electrophoresis

BACKGROUND

A new design of a flow-through coaxial electromembrane extraction (EME) probe that can be on-line coupled with CE instrument is described and tested. The supporting base of the probe is a PDMS microchip with T-shaped channels into which two coaxially arranged capillaries for inlet and outlet solutions are inserted. The extraction part of the probe is a porous polypropylene hollow fiber, sealed at one end and modified with nitrophenyloctyl ether (NPOE) extraction fluid. The internal volume of the extraction probe is 1.1 μL.

RESULTS

The EME probe was tested on laboratory samples and methadone was extracted into 3.0 M AcOH as acceptor. The concentration dependence was linear in the range of 0.1-1.0 μg mL-1 at EME 300 s/150 V and in the range of 0.5-10.0 μg mL-1 at EME 100 s/150 V. The enrichment factor was greater than 30 and the LOD was 0.21 μg mL-1. The EME of methadone in clinical samples showed a linear concentration dependence in human urine and a nonlinear concentration dependence in serum. The distribution of methadone in each phase of the extraction system and the effect of extraction membrane thickness on the enrichment factor were studied. The EME probe can be applied repeatedly.

SIGNIFICANCE

The supporting base of EME probe and flow gating interface (FGI) are realized by a microfluidic PDMS microchips cast in the laboratory without the use of lithography. A supporting PDMS chip with coaxially arranged capillaries and extraction membrane forms a compact analytical instrument. The entire EME/CE analysis process is performed on a laboratory-made instrument and automated by LabView.

Methadone for Cancer Pain Management in Children: A Review of Literature

Pain associated with cancer is a common feature among children and adolescents. Among opioids, methadone is a unique drug for its multiple mechanisms of action. Methadone is currently underutilized in children. The use of methadone for cancer pain management in children was assessed in a systematic review. Altogether, 141 children receiving methadone were examined, and another 126 children were assessed for QT prolongation. In the clinical studies, modalities of use, dosing, and duration of assessment were highly variable. In general, methadone was effective and well tolerated with a limited tendency for dose increases. QT prolongation was reported in a percentage of patients independently of the dosages or other variables. The majority of studies considered the use of methadone to be safe and effective in children. Despite methadone possessing interesting properties that make this drug unique in a pediatric context, data is limited, and the literature available is based on retrospective studies. Methadone could be an effective, inexpensive, and versatile medication in children with cancer who have pain. This drug deserves more interest and should prompt studies of better quality with a larger number of patients.

Combined in vivo metabolic effects of quetiapine and methadone in brain and blood of rats

Changes in pharmacokinetics and endogenous metabolites may underlie additive biological effects of concomitant use of antipsychotics and opioids. In this study, we employed untargeted metabolomics analysis and targeted analysis to examine the changes in drug metabolites and endogenous metabolites in the prefrontal cortex (PFC), midbrain, and blood of rats following acute co-administration of quetiapine and methadone. Rats were divided into four groups and received cumulative increasing doses of quetiapine (QTP), methadone (MTD), quetiapine + methadone (QTP + MTD), or vehicle (control). All samples were analyzed using liquid chromatography-mass spectrometry (LC-MS). Our findings revealed increased levels of the quetiapine metabolites: Norquetiapine, O-dealkylquetiapine, 7-hydroxyquetiapine, and quetiapine sulfoxide, in the blood and brain when methadone was present. Our study also demonstrated a decrease in methadone and its metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in the rat brain when quetiapine was present. Despite these findings, there were only small differences in the levels of 225-296 measured endogenous metabolites due to co-administration compared to single administrations. For example, N-methylglutamic acid, glutaric acid, p-hydroxyphenyllactic acid, and corticosterone levels were significantly decreased in the brain of rats treated with both compounds. Accumulation of serotonin in the midbrain was additionally observed in the MTD group, but not in the QTP + MTD group. In conclusion, this study in rats suggests a few but important additive metabolic effects when quetiapine and methadone are co-administered.

The amino acid metabolomics signature of differentiating myocardial infarction from strangulation death in mice models

This study differentiates myocardial infarction (MI) and strangulation death (STR) from the perspective of amino acid metabolism. In this study, MI mice model via subcutaneous injection of isoproterenol and STR mice model by neck strangulation were constructed, and were randomly divided into control (CON), STR, mild MI (MMI), and severe MI (SMI) groups. The metabolomics profiles were obtained by liquid chromatography-mass spectrometry (LC-MS)-based untargeted metabolomics. Principal component analysis, partial least squares-discriminant analysis, volcano plots, and heatmap were used for discrepancy metabolomics analysis. Pathway enrichment analysis was performed and the expression of proteins related to metabolomics was detected using immunohistochemical and western blot methods. Differential metabolites and metabolite pathways were screened. In addition, we found the expression of PPM1K was significantly reduced in the MI group, but the expression of p-mTOR and p-S6K1 were significantly increased (all P < 0.05), especially in the SMI group (P < 0.01). The expression of Cyt-C was significantly increased in each group compared with the CON group, especially in the STR group (all P < 0.01), and the expression of AMPKα1 was significantly increased in the STR group (all P < 0.01). Our study for the first time revealed significant differences in amino acid metabolism between STR and MI.

Intravenous Methadone for Perioperative and Chronic Cancer Pain: A Review of the Literature

Intravenous methadone may be useful in acute and chronic pain management compared with other opioids because of its pharmacokinetic and pharmacodynamic characteristics, including the long duration of effect and ability to modulate both pain stimuli propagation and analgesic descending pathways. However, methadone is underused in pain medicine because of several misperceptions. A review of studies was performed to assess data regarding the use of methadone in perioperative pain and chronic cancer pain. The majority of studies have shown that intravenous methadone produces an effective postoperative analgesia and lowers opioid consumption in the postoperative period, without more adverse effects in comparison with other opioid analgesics, and has an interesting potential to prevent persistent postoperative pain. A minority of studies investigated the use of intravenous methadone for cancer pain management. These studies were mostly case series that showed promising activities of intravenous methadone for difficult pain conditions. There is sufficient evidence suggesting that intravenous methadone is effective in perioperative pain, while more studies are needed in patients with cancer pain.

Abnormal fatty acid metabolism and ceramide expression may discriminate myocardial infarction from strangulation death: A pilot study

Determining myocardial infarction (MI) and mechanical asphyxia (MA) was one of the most challenging tasks in forensic practice. The present study aimed to investigate the potential of fatty acid (FAs) metabolism, and lipid alterations in determining MI and MA. MA and MI mouse models were constructed, and metabolic profiles were obtained by LC-MS-based untargeted metabolomics. The metabolic alterations were explored using the PCA, OPLS-DA, the Wilcoxon test, and fold change analysis. The contents of lipid droplets (LDs) were detected by the transmission scanning electron microscope and Oil red O staining. The immunohistochemical assay was performed to detect CD36 and dysferlin. The ceramide was assessed by LC-MS. PCA showed considerable differences in the metabolite profiles, and the well-fitting OPLS-DA model was developed to screen differential metabolites. Thereinto, 9 metabolites in the MA were reduced, while metabolites were up- and down-regulated in MI. The increased CD36 suggested that MI and MA could enhance the intake of FAs and disturb energy metabolism. The increased LDs, decreased dysferlin, and increased ceramide (C18:0, C22:0, and C24:0) were observed in MI groups, confirming the lipid deposition. The present study indicated significant differences in myocardial FAs metabolism and lipid alterations between MI and MA, suggesting that FAs metabolism and related proteins, certain ceramide may harbor the potential as biomarkers for discrimination of MI and MA.

Review of LC techniques for determination of methadone and its metabolite in the biological samples

Methadone (MTD) is a synthetic analgesic drug used for treating opioid dependence and effectively used clinically for patients with severe pain. The abuse of MTD may lead to poisoning, disorder in the central nervous system and even death. The regular monitoring of MTD in biological matrices including serum, plasma and urine samples is an effective way to control abuse of MTD. In this manner, the selection of analytical monitoring of MTD in biological matrices is of paramount importance. This study was conducted to review high-performance liquid chromatography (HPLC) techniques carried out on MTD and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in the biological samples during 2015-June 2021.

Metabolic phenotyping of opioid and psychostimulant addiction: A novel approach for biomarker discovery and biochemical understanding of the disorder

Despite the progress in characterising the pharmacological profile of drugs of abuse, their precise biochemical impact remains unclear. The metabolome reflects the multifaceted biochemical processes occurring within a biological system. This includes those encoded in the genome but also those arising from environmental/exogenous exposures and interactions between the two. Using metabolomics, the biochemical derangements associated with substance abuse can be determined as the individual transitions from recreational drug to chronic use (dependence). By understanding the biomolecular perturbations along this time course and how they vary across individuals, metabolomics can elucidate biochemical mechanisms of the addiction cycle (dependence/withdrawal/relapse) and predict prognosis (recovery/relapse). In this review, we summarise human and animal metabolomic studies in the field of opioid and psychostimulant addiction. We highlight the importance of metabolomics as a powerful approach for biomarker discovery and its potential to guide personalised pharmacotherapeutic strategies for addiction targeted towards the individual's metabolome.

Exploring metabolic alterations associated with death from asphyxia and the differentiation of asphyxia from sudden cardiac death by GC-HRMS-based untargeted metabolomics

The determination of cause of death is one of the most important tasks in forensic practice. However, asphyxia is a difficult cause of death to determine, especially when the deceased has an underlying disease that can lead to a sudden unexpected death, such as coronary atherosclerotic heart disease (CAHD, which is the leading cause of sudden cardiac death, SCD), because its determination is currently still based on an exclusion strategy. In this study, gas chromatography coupled with high-resolution mass spectrometry (GC-HRMS)-based untargeted metabolomics was employed to obtain the pulmonary metabolic profiles of rats who died from asphyxia and SCD. First, fourteen metabolites were identified to investigate the mechanism of death from asphyxia, and we proposed some explanations that may account for these metabolic alterations, including the perturbation of amino acid metabolism, lipid metabolism, and energy metabolism (TCA cycle). Second, we discovered eight potential biomarkers to differentiate between asphyxia and SCD as the cause of death. The excellent classification performances of the eight individual biomarkers and their combination in fresh lung tissue were observed. Third, we also explored the relative change in the concentration of the eight metabolites and their classification performance in decomposed tissue (at 24 h postmortem). Lactic acid, pantothenic acid, and the combination of the eight biomarkers can be recognized as perfect classifiers to discriminate asphyxia from SCD even when decomposition has occurred. Our results showed that GC-HRMS-based untargeted metabolomics can be used as a promising tool to explore the metabolic alterations of the death process and to determine the cause of death.

Quantification of methadone and its metabolites: EDDP and EMDP determined in autopsy cases using LC-MS/MS

The paper presents a method for the determination of methadone, EDDP, and EMDP in postmortem biological materials using liquid-liquid extraction with ethyl acetate (pH9) and UHPLC-MS/MS technique. Methadone-d₉ and EDDP-d₃ were used as the internal standards. The method validation results for blood and urine were as follows: linearity: 0.5-1000 ng/ml; R²  > 0.9993 for methadone, EDDP and R²  > 0.9944 for EMDP. Intra- and inter-day precision: 0.1%-7.5% and 0.3%-8.6%, respectively; intra- and inter-day accuracy: -11.8% to 13.9% and -9.3 to 14.8%, respectively; recovery: 91.5%-123.0%; matrix effect: 83.5%-123.9%. This study also describes 18 postmortem cases, where methadone concentrations ranged 2.3-1180 ng/ml in blood (n = 17), from 11.0 to >10,000 ng/ml in urine (n = 13) and 135.2-409.0 in vitreous humor (VH, n = 3). EDDP concentrations ranged from not detectable to 180 ng/mL in blood, from 42.4 to >10,000 ng/ml in urine and 18.3-36.5 in VH. EMDP concentrations were found in four cases in blood from below LLOQ to 1.8 ng/ml and in seven cases in urine, ranged 2.1-243.0 ng/ml. EMDP was not detected in VH samples. The EDDP/methadone ratios and blood/urine ratios for methadone and EDDP in EMDP-positive and negative cases were performed. The paper presents mass spectra of other methadone metabolites, than EDDP and EMDP (ring hydroxylated methadone, ring hydroxylated EDDP, ring hydroxylated EMDP, methadol, and DDP). Simultaneous determination of methadone and its metabolites in order to unequivocally interpret the results of toxicological tests seems to be useful in cases related to prescription/illicit use of methadone.

The Use of Gas Chromatography Coupled with High-Resolution Mass Spectrometry-Based Untargeted Metabolomics to Discover Metabolic Changes and Help in the Determination of Complex Causes of Death: A Preliminary Study

The determination of cause of death (COD) is one of the most important tasks in forensic practice and is mainly based on macroscopical and microscopical morphological signatures. However, some CODs are hard to determine because the significant morphological signatures can be nonspecific, variable, subjective, or even absent in the real world. In this study, gas chromatography coupled with high-resolution mass spectrometry (GC-HRMS)-based untargeted metabolomics was employed to obtain plasma metabolic profiles of rats that died from anaphylactic shock (AS), mechanical asphyxia (MA), or sudden cardiac death (SCD). The metabolic alterations of each COD group compared to the control group were investigated using a principal component analysis, partial least-squares discriminant analysis, the Wilcoxon test, and fold change analysis. A range of differential features was screened, and 11, 8, and 7 differential metabolites were finally verified for the AS, MA, and SCD groups, respectively. We proposed some explanations that may account for these metabolic differences, including glucose metabolism, the tricarboxylic acid cycle, glycolysis, lipid metabolism, creatinine catabolism, and purine metabolism. Next, for each COD, we used its differential metabolites, which were obtained through comparisons of each COD group to the control group and represented the metabolic changes of the individual COD, to perform a receiver operating characteristic (ROC) analysis to preliminarily evaluate their ability to discriminate each COD group from the other COD groups. We found that creatinine in the AS group and malic acid and uric acid in the MA group might represent some specific metabolic changes for the relevant COD with high areas under the curve in the ROC curve analysis. Moreover, the combination panel for AS or MA also showed a good ability to discriminate it from the others. However, SCD had fewer metabolic signatures and was relatively harder to discriminate from the other CODs in our work. The preliminary study demonstrates the feasibility of GC-HRMS-based untargeted metabolomics as a promising tool to reveal metabolic changes in different death processes and to determine the complex CODs.

Methadone for Pain Management: A Pharmacotherapeutic Review

Methadone is increasingly being used for its analgesic properties. Despite the increasing popularity, many healthcare providers are not familiar with methadone's complex pharmacology and best practices surrounding its use. The purpose of this narrative review article is to discuss the pharmacology of methadone, the evidence surrounding methadone's use in acute pain management and both chronic cancer and non-cancer pain settings, as well as highlight pertinent safety, monitoring, and opioid rotation considerations. Methadone has a unique mechanism of action when compared with all other opioids and for this reason methadone has come to hold a niche role in the management of opioid-induced hyperalgesia and central sensitization. Understanding of the mechanisms of variability in methadone disposition and drug interactions has evolved over the years, with the latest evidence revealing that CYP 2B6 is the major determinant of methadone elimination and plays a key role in methadone-related drug interactions. From an acute pain perspective, most studies evaluating the use of intraoperative intravenous methadone have reported lower pain scores and post-operative opioid requirements. Oral methadone is predominantly used as a second-line opioid treatment for select chronic pain conditions. As a result, several oral morphine to oral methadone conversion ratios have been proposed, as have methods in which to rotate to methadone. From an efficacy standpoint, limited literature exists regarding the effectiveness of methadone in the chronic pain setting with most of the available efficacy data pertaining to methadone's use in the treatment of cancer pain. Many of the prospective studies that exist feature low participant numbers. Few clinical trials investigating the role of methadone as an analgesic treatment are currently underway. The complicated pharmacokinetic properties of methadone and risks of harm associated with this drug highlight how critically important it is that healthcare providers understand these features before prescribing/dispensing methadone. Particular caution is required when converting patients from other opioids to methadone and for this reason only experienced healthcare providers should undertake such a task. Further randomized trials with larger sample sizes are needed to better define the effective and safe use of methadone for pain management.

Pharmacokinetic and Pharmacodynamic Aspects of Peyote and Mescaline: Clinical and Forensic Repercussions

BACKGROUND

Mescaline (3,4,5-trimethoxyphenethylamine), mainly found in the Peyote cactus (Lophophora williamsii), is one of the oldest known hallucinogenic agents that influence human and animal behavior, but its psychoactive mechanisms remain poorly understood.

OBJECTIVES

This article aims to fully review pharmacokinetics and pharmacodynamics of mescaline, focusing on the in vivo and in vitro metabolic profile of the drug and its implications for the variability of response.

METHODS

Mescaline pharmacokinetic and pharmacodynamic aspects were searched in books and in PubMed (U.S. National Library of Medicine) without a limiting period. Biological effects of other compounds found in peyote were also reviewed.

RESULTS

Although its illicit administration is less common, in comparison with cocaine and Cannabis, it has been extensively described in adolescents and young adults, and licit consumption often occurs in religious and therapeutic rituals practiced by the Native American Church. Its pharmacodynamic mechanisms of action are primarily attributed to the interaction with the serotonergic 5-HT2A-C receptors, and therefore clinical effects are similar to those elicited by other psychoactive substances, such as lysergic acid diethylamide (LSD) and psilocybin, which include euphoria, hallucinations, depersonalization and psychoses. Moreover, as a phenethylamine derivative, signs and symptoms are consistent with a sympathomimetic effect. Mescaline is mainly metabolized into trimethoxyphenylacetic acid by oxidative deamination but several minor metabolites with possible clinical and forensic repercussions have also been reported.

CONCLUSION

Most reports concerning mescaline were presented in a complete absence of exposure confirmation, since toxicological analysis is not widely available. Addiction and dependence are practically absent and it is clear that most intoxications appear to be mild and are unlikely to produce lifethreatening symptoms, which favors the contemporary interest in the therapeutic potential of the drugs of the class.

Optimisation of methadone treatment in a group of patients on a mephedrone binge and dependent on many psychoactive substances

Objectives: In recent years, an increase in the frequency of hospitalisations of patients on a mephedrone binge has been observed. The literature lacks data on the optimisation of methadone treatment in this group of people.Methods: The study included 601 patients who took mephedrone on a regular basis between 2010 and 2018. Based on the pharmacological database created, it was verified which methadone interaction contributed to subsequent hospitalisations in the group of people studied and which of them had the best therapeutic effect.Results: During the study, 62.4% of patients received methadone (p < .001). The higher the number of drugs taken together with methadone, the higher the frequency of hospitalisations (p < .001). The highest frequency of re-hospitalisations was recorded in patients who combined mephedrone with at least two other psychoactive substances, as well as those who used methadone with chlorprothixene (p < .001). The most optimal therapeutic effect is characteristic for the intake of methadone with thiazolidine carboxylic acid, namely 95% of people using this type of treatment were hospitalised once (p < .001).Conclusions: Therapy with methadone and thiazolidine carboxylic acid seems to be the most optimal therapy for patients taking mephedrone.Key pointsThe number of hospitalisations of patients receiving mephedrone on a regular basis grows from year to year.The multiple use of poly-pharmacotherapy increased in a group of patients on a mephedrone binge.There is a statistically significant correlation between the number of hospitalisations of patients on a mephedrone binge and the total number of drugs taken together with methadone.Administration of methadone with thiazolidine carboxylic acid was the most effective therapy for patients regularly combining mephedrone with at least two other psychoactive substances.

New and Enzymatic Targeted Magnetic Macromolecular Nanodrug System Which Delivers Methadone and Rifampin Simultaneously

An indicator for cytochrome P450 (CYP-450) enzymes includes CYP-450 which has the most fundamental role in methadone metabolism in the liver. The aim of this study is to design and interface a macromolecular nanodrug system to deliver rifampin (RIF) and methadone (MTD) simultaneously to the liver based on magnetic nanoparticles (MNPs). RIF increases the metabolism of MTD in the liver. In this study, MTD was linked to a magnetic nanocapsule including RIF by a heterocyclic linker. This heterocyclic linker was prepared in five steps. Fourier transform infrared spectroscopy and NMR indicated the synthesis of the heterocyclic linker, scanning electron microscopy and confocal fluorescence microscopy exhibited the morphology of NPs and loading MTD. Atomic force microscopy was applied to indicate the three-dimensional topology of NPs and the conglomeration on them. Magnetization properties of loaded and unloaded NPs were characterized by vibrating-sample magnetometer. These patterns indicated superparamagnetic properties of MNPs therefore these NPs do not retain any magnetism after removal of a magnetic field. In vitro release studies of RIF and MTD by UV-vis measurements in several buffer solutions demonstrated that behavior of drug release is related to pH. The histopathology study was performed on the liver of rats injected with MTD, morphine (MOR), and the prepared drug. Cytotoxicity of the prepared sample on MCF-7 cell line assay was assessed via 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide solution. The histopathology study indicated that the cotreatment of the synthesized drug attenuated hepatic lesions. Delivery of RIF and MTD simultaneously to the liver by MNPs (1) increases MTD metabolism because of increasing CYP-450 enzymes induced by RIF and (2) decreases hepatic lesions via injection of the synthesized drug with cotreatment by MOR.

Mitragynine Attenuates Morphine Withdrawal Effects in Rats-A Comparison With Methadone and Buprenorphine

BACKGROUND

Opiate addiction is a major health problem in many countries. A crucial component of the medical treatment is the management of highly aversive opiate withdrawal signs, which may otherwise lead to resumption of drug taking. In a medication-assisted treatment (MAT), methadone and buprenorphine have been implemented as substitution drugs. Despite MAT effectiveness, there are still limitations and side effects of using methadone and buprenorphine. Thus, other alternative therapies with less side effects, overdosing, and co-morbidities are desired. One of the potential pharmacotherapies may involve kratom's major indole alkaloid, mitragynine, since kratom (Mitragyna speciosa Korth.) preparations have been reported to alleviate opiate withdrawal signs in self-treatment in Malaysian opiate addicts.

METHODS

Based on the morphine withdrawal model, rats were morphine treated with increasing doses from 10 to 50 mg/kg twice daily over a period of 6 days. The treatment was discontinued on day 7 in order to induce a spontaneous morphine abstinence. The withdrawal signs were measured daily after 24 h of the last morphine administration over a period of 28 abstinence days. In rats that developed withdrawal signs, a drug replacement treatment was given using mitragynine, methadone, or buprenorphine and the global withdrawal score was evaluated.

RESULTS

The morphine withdrawal model induced profound withdrawal signs for 16 days. Mitragynine (5-30 mg/kg; i.p.) was able to attenuate acute withdrawal signs in morphine dependent rats. On the other hand, smaller doses of methadone (0.5-2 mg/kg; i.p.) and buprenorphine (0.4-1.6 mg/kg; i.p.) were necessary to mitigate these effects.

CONCLUSIONS

These data suggest that mitragynine may be a potential drug candidate for opiate withdrawal treatment.

Composite score analysis for unsupervised comparison and network visualization of metabolomics data

Metabolomics-based approaches are becoming increasingly popular to interrogate the chemical basis for phenotypic differences in biological systems. Successful metabolomics studies employ multivariate data analysis to compare large and highly complex datasets. A primary tool for unsupervised statistical analyses, principal component analysis (PCA), relies on the selection of a subsection of a maximum of three components from a larger model to visually represent similarity. The use of only three principal components limits the comprehensiveness of the model and can mask discrimination between samples. We have developed a new statistical metric, the composite score (CS), as a univariate statistic that incorporates multiple principal components to calculate a correlation matrix that enables quantitative comparisons of sample similarity between samples within one dataset based upon measured metabolome profiles. Composite score values were tabulated using profiles of complex extracts of dietary supplements from the plant Hydrastis canadensis (goldenseal) as a case study. Several outliers were unambiguously identified, and a PCA composite score network was developed to provide a graphical representation of the composite score matrix. Comparison with visualization using PCA score plots or dendrograms from hierarchical clustering analysis (HCA) demonstrates the utility of the composite score to as a tool for metabolomics studies that seek to quantify similarity among samples. An R-script for the calculation of composite score has been made available.

A Sensitive LC-MS/MS Assay for the Quantification of Methadone and its Metabolites in Dried Blood Spots: Comparison With Plasma

INTRODUCTION

Methadone, a synthetic narcotic, is widely used both in adults and children for pain control and as a replacement drug in opioid use disorder to prevent craving and withdrawal. To support clinical pharmacokinetic trials in neonates, infants, and children, the authors developed and validated a novel, automated, highly sensitive liquid chromatography-electrospray-tandem mass spectrometry ionization (LC-ESI-MS/MS) method for the quantification of methadone and its metabolites, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenylpyraline (EMDP), in samples collected as dried blood spots.

METHODS

Blood was spiked with different concentrations of methadone, EDDP, and EMDP, and blood drops were applied to filter paper cards. Punches of 6.4 mm were removed from the cards, and 600 µL of protein precipitation solution (methanol/0.2M ZnSO4, 7:3, vol/vol) containing the internal standards (methadone-d9 and EDDP-d5) at a concentration of 1 mcg/L was added. The extracts were analyzed using LC-ESI-MS/MS in combination with online extraction. The mass spectrometer was run in the positive multiple reaction monitoring mode, and the total run time was 3.2 minutes.

RESULTS

For the dried blood spots, the assay has a lower limit of quantification of 0.1 mcg/L for methadone, EDDP, and EMDP. The range of reliable response for methadone for the ion transition m/z = 310.2→265.1 was 0.1-100 mcg/L and for the ion transition m/z = 310.2→223.1 5-1000 mcg/L. For EDDP, on the range of reliable response for the ion transition, m/z = 278.2→234.3 was 0.1-100 mcg/L and for the ion transition m/z = 278.2→186.1 5-1000 mcg/L. The calibration range for EMDP was 0.1-100 mcg/L. Accuracy (85%-115%) and imprecision (<15%) met predefined acceptance criteria.

DISCUSSION

This assay allows for the measurement of small volume blood samples without the need for an intravenous blood draw, and thus, it is suitable for pharmacokinetics studies and therapeutic drug monitoring in pediatric patients.

Metabolomic Strategies in Biomarker Research-New Approach for Indirect Identification of Drug Consumption and Sample Manipulation in Clinical and Forensic Toxicology?

Drug of abuse (DOA) consumption is a growing problem worldwide, particularly with increasing numbers of new psychoactive substances (NPS) entering the drug market. Generally, little information on their adverse effects and toxicity are available. The direct detection and identification of NPS is an analytical challenge due to their ephemerality on the drug scene. An approach that does not directly focus on the structural detection of an analyte or its metabolites, would be beneficial for this complex analytical scenario and the development of alternative screening methods could help to provide fast response on suspected NPS consumption. A metabolomics approach might represent such an alternative strategy for the identification of biomarkers for different questions in DOA testing. Metabolomics is the monitoring of changes in small (endogenous) molecules (<1,000 Da) in response to a certain stimulus, e.g., DOA consumption. For this review, a literature search targeting "metabolomics" and different DOAs or NPS was conducted. Thereby, different applications of metabolomic strategies in biomarker research for DOA identification were identified: (a) as an additional tool for metabolism studies bearing the major advantage that particularly a priori unknown or unexpected metabolites can be identified; and (b) for identification of endogenous biomarker or metabolite patterns, e.g., for synthetic cannabinoids or also to indirectly detect urine manipulation attempts by chemical adulteration or replacement with artificial urine samples. The majority of the currently available literature in that field, however, deals with metabolomic studies for DOAs to better assess their acute or chronic effects or to find biomarkers for drug addiction and tolerance. Certain changes in endogenous compounds are detected for all studied DOAs, but often similar compounds/pathways are influenced. When evaluating these studies with regard to possible biomarkers for drug consumption, the observed changes appear, albeit statistically significant, too small to reliably work as biomarker for drug consumption. Further, different drugs were shown to affect the same pathways. In conclusion, metabolomic approaches possess potential for detection of biomarkers indicating drug consumption. More studies, including more sensitive targeted analyses, multi-variant statistical models or deep-learning approaches are needed to fully explore the potential of omics science in DOA testing.

Expanding Role of NMDA Receptor Antagonists in the Management of Pain

Pain management is complex regardless of whether the pain is acute or chronic in nature or non-cancer or cancer related. In addition, relatively few pain pharmacotherapy options with adequate efficacy and safety data currently exist. Consequently, interest in the role of NMDA receptor antagonists as a pharmacological pain management strategy has surfaced. This narrative review provides an overview of the NMDA receptor and elaborates on the pharmacotherapeutic profile and pain management literature findings for the following NMDA receptor antagonists: ketamine, memantine, dextromethorphan, and magnesium. The literature on this topic is characterized by small studies, many of which exhibit methodological flaws. To date, ketamine is the most studied NMDA receptor antagonist for both acute and chronic pain management. Although further research about NMDA receptor antagonists for analgesia is needed and the optimal dosage/administration regimens for these drugs have yet to be determined, ketamine appears to hold the most promise and may be of particular value in the perioperative pain management realm.

Pharmacologic Treatment of Opioid Use Disorder: a Review of Pharmacotherapy, Adjuncts, and Toxicity

Opioid use disorder continues to be a significant source of morbidity and mortality in the USA and the world. Pharmacologic treatment with methadone and buprenorphine has been shown to be effective at retaining people in treatment programs, decreasing illicit opioid use, decreasing rates of hepatitis B, and reducing all cause and overdose mortality. Unfortunately, barriers exist in accessing these lifesaving medications: users wishing to start buprenorphine therapy require a waivered provider to prescribe the medication, while some states have no methadone clinics. As such, users looking to wean themselves from opioids or treat their opioid dependence will turn to alternative agents. These agents include using prescription medications, like clonidine or gabapentin, off-label, or over the counter drugs, like loperamide, in supratherapeutic doses. This review provides information on the pharmacology and the toxic effects of pharmacologic agents that are used to treat opioid use disorder. The xenobiotics reviewed in depth include buprenorphine, clonidine, kratom, loperamide, and methadone, with additional information provided on lofexidine, akuamma seeds, kava, and gabapentin.

Histopathological study of liver tissue due to methadone consumption and its effect on liver enzymes and inflammatory indices in rat

Background

Methadone (MET)-based treatment is currently one of the best known approaches in the treatment of opioid dependence. It is claimed that MET use exerts adverse effects on the performance of some organs, especially liver. Thus, the present study aims to investigate MET effects on the hepatic tissue as well as its effect on the hepatic enzyme levels and inflammatory markers in rats.

Materials and methods

Twenty-eight mature male Wistar rats underwent an 8-week treatment in four equal groups including the control group (an ordinary daily dietary regime) as well as the experimental groups 1, 2, and 3 (an ordinary daily dietary regime and gavage-fed on MET syrup for 5, 20, and 40 mg/kg body weight per day). Blood samples were collected from all rats in the beginning and end of the study to measure their hepatic enzyme levels and inflammatory markers. In the end, their livers were subjected to histological examinations.

Results

The mean serum levels of hepatic enzymes (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase) increased considerably across all the three groups that had received various dosages of MET (5, 20, and 40 mg/kg) in the end of the study as compared to the beginning of the study (P<0.001). It was also found that the inflammatory indicators (interleukin-6, tumor necrosis factor-alpha, and C-reactive protein) rose significantly in the groups that had received various dosages of MET in contrast to the control group (P<0.01, P<0.001, and P<0.001, respectively). The histopathological images of the liver cross-sections revealed dosage-dependent tissue changes in the groups that had received various dosages of MET.

Conclusion

The present study tried to prove the adverse effects of MET in the development of liver damage. Since MET-based treatment is frequently prescribed by physicians for curing the addiction to narcotics, better strategies are required for its correct usage.

Metabolic Profiles of Propofol and Fospropofol: Clinical and Forensic Interpretative Aspects

Propofol is an intravenous short-acting anesthetic widely used to induce and maintain general anesthesia and to provide procedural sedation. The potential for propofol dependency and abuse has been recognized, and several cases of accidental overdose and suicide have emerged, mostly among the health professionals. Different studies have demonstrated an unpredictable interindividual variability of propofol pharmacokinetics and pharmacodynamics with forensic and clinical adverse relevant outcomes (e.g., pronounced respiratory and cardiac depression), namely, due to polymorphisms in the UDP-glucuronosyltransferase and cytochrome P450 isoforms and drugs administered concurrently. In this work the pharmacokinetics of propofol and fospropofol with particular focus on metabolic pathways is fully reviewed. It is concluded that knowing the metabolism of propofol may lead to the development of new clues to help further toxicological and clinical interpretations and to reduce serious adverse reactions such as respiratory failure, metabolic acidosis, rhabdomyolysis, cardiac bradyarrhythmias, hypotension and myocardial failure, anaphylaxis, hypertriglyceridemia, renal failure, hepatomegaly, hepatic steatosis, acute pancreatitis, abuse, and death. Particularly, further studies aiming to characterize polymorphic enzymes involved in the metabolic pathway, the development of additional routine forensic toxicological analysis, and the relatively new field of ‘‘omics” technology, namely, metabolomics, can offer more in explaining the unpredictable interindividual variability.

Quantification of Methadone and Main Metabolites in Nails

The quantification of drugs of abuse in keratinized matrices is becoming of special relevance for monitoring consumption and for post-mortem investigations. We aimed to implement an analytical method for the simultaneous detection of morphine (MORF), 6-monoacetylmorphine (6-MAM), methadone (MET), 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenylpyrrolidine (EMDP) in nails. After decontamination, the nail samples (30 mg) were submitted to an alkaline digestion followed by a two-step liquid-liquid and SPE extraction using mixed-mode cation exchange cartridges. The analytes were eluted with 5% NH4OH/methanol. After derivatization with N-methyl-N-(trimethylsilyl) trifluoroacetamide, the analytes were quantified by gas chromatography-mass spectrometry. The method was optimized and fully validated only for MET, EDDP and EMDP, since for MOR and 6-MAM it was not possible to obtain adequate recovery rates after extraction, although detection of MOR was still possible. The method was selective, accurate and precise. Regression analysis demonstrated linearity over a concentration range of 20.8-333.3 ng/mg for MET and 10.4-166.7 ng/mg for EDDP and EMDP. Limits of detection and quantification values ranged from 3.3 to 6.0 ng/mg and 10.4 to 20.8 ng/mg, respectively, and recovery rates ranged from 82% to 98%. The applicability of the method was demonstrated by analyzing nail and urine samples obtained from heroin consumers under substitution therapy with MET.

The synthetic cathinone α-pyrrolidinovalerophenone (α-PVP): pharmacokinetic and pharmacodynamic clinical and forensic aspects

New psychoactive substances (NPS), often referred as 'legal highs' or 'designer drugs', are derivatives and analogs of existing psychoactive drugs that are introduced in the recreational market to circumvent existing legislation on drugs of abuse. This work aims to review the state-of-the-art regarding chemical, molecular pharmacology, and in vitro and in vivo data on toxicokinetics of the potent synthetic cathinone α-pyrrolidinovalerophenone (α-PVP or flakka or zombie drug). Chemical, pharmacological, toxicological, and clinical effects of α-PVP were searched in PubMed (U.S. National Library of Medicine) and governmental websites without limitation of the period. α-PVP is a wide spread and easy to get special type of synthetic cathinone with seemingly powerful cocaine-like stimulant effects, high brain penetration, high liability for abuse and with increased risk of adverse effects such as tachycardia, agitation, hypertension, hallucinations, delirium, mydriasis, self-injury, aggressive behavior, and suicidal ideations. α-PVP undergoes extensive metabolism via different pathways and the α-PVP itself or its metabolites β-hydroxy-α-PVP and α-PVP lactam represent the main targets for toxicological analysis in urine. There is a limited knowledge regarding the short- and long-term effects of α-PVP and metabolites, and pharmacogenetic influence, hence further clinical and forensic toxicological studies are required. Moreover, since α-PVP cannot be detected with classic routine analysis procedures, statements on the frequency of their consumption cannot be made.

Effects of cytochrome P450 single nucleotide polymorphisms on methadone metabolism and pharmacodynamics

Methadone is a synthetic, long-acting opioid with a single chiral center forming two enantiomers, (R)-methadone and (S)-methadone, each having specific pharmacological actions. Concentrations of (R)- and (S)-methadone above therapeutic levels have the ability to cause serious, life-threatening, and fatal side effects. This toxicity can be due in part to the pharmacogenetics of an individual, which influences the pharmacokinetic and pharmacodynamic properties of the drug. Methadone is primarily metabolized in the liver by cytochrome P450 (CYP) enzymes, predominately by CYP2B6, followed by CYP3A4, 2C19, 2D6, and to a lesser extent, CYP2C18, 3A7, 2C8, 2C9, 3A5, and 1A2. Single nucleotide polymorphisms (SNPs) located within CYPs have the potential to play an important role in altering methadone metabolism and pharmacodynamics. Several SNPs in the CYP2B6, 3A4, 2C19, 2D6, and 3A5 genes result in increases in methadone plasma concentrations, decreased N-demethylation, and decreased methadone clearance. In particular, carriers of CYP2B6*6/*6 may have a greater risk for detrimental adverse effects, as methadone metabolism and clearance are diminished in these individuals. CYP2B6*4, on the other hand, has been observed to decrease plasma concentrations of methadone due to increased methadone clearance. The involvement, contribution, and understanding the role of SNPs in CYP2B6, and other CYP genes, in methadone metabolism can improve the therapeutic uses of methadone in patient outcome and the development of personalized medicine.

Metabolism and metabolomics of ketamine: a toxicological approach

Ketamine is a phencyclidine derivative and a non-competitive antagonist of N-methyl-D-aspartate (NMDA) receptor for which glutamate is the full agonist. It produces a functional dissociation between the thalamocortical and limbic systems, a state that has been termed as dissociative anaesthesia. Considerable variability in the pharmacokinetics and pharmacodynamics between individuals that can affect dose-response and toxicological profile has been reported. This review aims to discuss pharmacokinetics of ketamine, namely focusing on all major and minor, active and inactive metabolites. Both ketamine optical isomers undergo hepatic biotransformation through the cytochrome P450, specially involving the isoenzymes 3A4 and 2B6. It is first N-demethylated to active metabolite norketamine. Different minor pathways have been described, namely hydroxylation of the cyclohexanone ring of ketamine and norketamine, and further conjugation with glucuronic acid to increase renal excretion. More recently, metabolomics data evidenced the alteration of several biological pathways after ketamine administration such as glycolysis, tricarboxylic acid cycle, amino acids metabolism and mitochondrial β-oxidation of fatty acids. It is expected that knowing the metabolism and metabolomics of ketamine may provide further insights aiming to better characterize ketamine from a clinical and forensic perspective.