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Synthetic cathinones are the second largest group of new psychoactive substances (NPS) monitored by the European Monitoring Centre for Drugs and Drug Addiction. Although 3-methylmethcathinone (3-MMC, C 11 H 15 NO) is legally banned in many countries, it is readily available for purchase online and on the street. Due to the scarcity of information regarding the pharmacokinetic and toxicological profile of 3-MMC, understanding its biotransformation pathways is crucial in determining its potential toxicity in humans and in the development of analytical methods for screening of human matrices. To gain more insight, Phase I and Phase II in vitro biotransformation of 3-MMC was investigated using human liver microsomes and human liver cytosol. Suspect and non-target screening approaches were employed to identify metabolites. To confirm in vitro results in an in vivo setting, human matrices (i.e., plasma, urine, saliva and hair) positive for 3-MMC (n=31) were screened. In total three biotransformation products were identified in vitro: C 11 H 15 NO 2 (a hydroxylated derivate), C 11 H 17 NO (a keto-reduced derivate) and C 10 H 13 NO (an N-desmethyl derivate). All three were confirmed as human metabolites in respectively 16 %, 52 % and 42 % of the analysed human samples. In total, 61 % of the analysed samples were positive for at least one of the three metabolites. Interestingly, three urine samples were positive for all three metabolites. The presence of 3-MMC in saliva and hair indicates its potential applicability in specific settings, e.g., roadside testing or chronic consumption analysis. To our knowledge, C 11 H 17 NO was not detected before in vivo. Although some of these metabolites have been previously suggested in vitro or in a single post mortem case report, a wide in vivo confirmation including the screening of four different human matrices was performed for the first time. These metabolites could serve as potential human biomarkers to monitor human 3-MMC consumption effectively., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Synthetic cathinones represent one of the largest and most abused new psychoactive substance classes, and have been involved in numerous intoxications and fatalities worldwide. Methcathinone analogues like 3-methylmethcathinone (3-MMC), 3-chloromethcathinone (3-CMC), and 4-CMC currently constitute most of synthetic cathinone seizures in Europe. Documenting their consumption in clinical/forensic casework is therefore essential to tackle this trend. Targeting metabolite markers is a go-to to document consumption in analytical toxicology, and metabolite profiling is crucial to support investigations. We sought to identify 3-CMC, 4-CMC, and 4-bromomethcathinone (4-BMC) human metabolites. The substances were incubated with human hepatocytes; incubates were screened by liquid chromatography-high-resolution tandem mass spectrometry and data were mined with Compound Discoverer (Themo Scientific). 3-CMC-positive blood, urine, and oral fluid and 4-CMC-positive urine and saliva from clinical/forensic casework were analyzed. Analyses were supported by metabolite predictions with GLORYx freeware. Twelve, ten, and ten metabolites were identified for 3-CMC, 4-CMC, and 4-BMC, respectively, with similar transformations occurring for the three cathinones. Major reactions included ketoreduction and N-demethylation. Surprisingly, predominant metabolites were produced by combination of N-demethylation and ω-carboxylation (main metabolite in 3-CMC-positive urine), and combination of β-ketoreduction, oxidative deamination, and O-glucuronidation (main metabolite in 4-CMC-positive urine). These latter metabolites were detected in negative-ionization mode only and their non-conjugated form was not detected after glucuronide hydrolysis; this metabolic pathway was never reported for any methcathinone analogue susceptible to undergo the same transformations. These results support the need for comprehensive screening strategies in metabolite identification studies, to avoid overlooking significant metabolites and major markers of consumption., (© 2024. The Author(s).)

Background and Objectives: Whole-body radiation exposure has been shown to alter the pharmacokinetics of certain drugs in both animal models and humans, but little is known about the effect of radiation on psychoactive medications. These drugs may have altered pharmacokinetics when administered during or after space travel or therapeutic or accidental radiation exposure, resulting in reduced efficacy or increased toxicity., Methods: Methamphetamine was used to determine the effects of acutely administered 1, 3, and 6 Gy radiation on drug pharmacokinetics and pharmacodynamics. Male Wistar rats were exposed to 0, 1, 3, or 6 Gy X-ray radiation on day 0. The serum pharmacokinetics of subcutaneously administered 1 mg/kg methamphetamine was determined on day 3. Methamphetamine-induced (1 mg/kg) locomotor activity was measured on day 5. Brain methamphetamine concentrations were determined 2 h after methamphetamine administration (1 mg/kg) on day 6. Renal and hepatic serum biomarkers were assessed on days 3 and 6, with liver histology performed on day 6., Results: While serum half-life and unchanged methamphetamine urine clearance were unaffected by any radiation dose, maximum methamphetamine concentrations and methamphetamine and amphetamine metabolite area under the serum concentration-time curve values from 0 to 300 min were significantly reduced after 6 Gy radiation exposure. Additionally, methamphetamine-induced locomotor activity and the brain to serum methamphetamine concentration ratio were significantly elevated after 6 Gy radiation., Conclusions: While 1-6 Gy radiation exposure did not affect methamphetamine elimination, 6 Gy exposure had effects on both subcutaneous absorption and brain distribution. These effects should be considered when administering drugs during or after radiation exposure., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Methiopropamine is a novel psychoactive substance (NPS) that is associated with several cases of clinical toxicity, yet little information is available regarding its neuropharmacological properties. Here, we employed in vitro and in vivo methods to compare the pharmacokinetics and neurobiological effects of methiopropamine and its structural analog methamphetamine. Methiopropamine was rapidly distributed to the blood and brain after injection in C57BL/6 mice, with a pharmacokinetic profile similar to that of methamphetamine. Methiopropamine induced psychomotor activity, but higher doses were needed (E max 12.5 mg/kg; i.p.) compared to methamphetamine (E max 3.75 mg/kg; i.p.). A steep increase in locomotor activity was seen after a modest increase in the methiopropamine dose from 10 to 12.5 mg/kg, suggesting that a small increase in dosage may engender unexpectedly strong effects and heighten the risk of unintended overdose in NPS users. In vitro studies revealed that methiopropamine mediates its effects through inhibition of norepinephrine and dopamine uptake into presynaptic nerve terminals (IC 50 = 0.47 and 0.74 µM, respectively), while the plasmalemmal serotonin uptake and vesicular uptake are affected only at high concentrations (IC 50 > 25 µM). In summary, methiopropamine closely resembles methamphetamine with regard to its pharmacokinetics, pharmacodynamic effects and mechanism of action, with a potency that is approximately five times lower than that of methamphetamine.

Background and Objectives: Approximately 10 years ago, "bath salts" became popular as legal alternatives to the psychostimulants cocaine and the amphetamines. These products contained synthetic cathinones, including 3,4-methylenedioxypyrovalerone (MDPV), 4-methylmethcathinone (mephedrone), and 3,4-methylenedioxymethcathinone (methylone). Most preclinical investigations have only assessed the effects of these synthetic cathinones independently; however, case reports and Drug Enforcement Administration (DEA) studies indicate that bath salts contain mixtures of these substances. In this study, we examine the pharmacokinetic interactions of the drug combination. We hypothesized that combined exposure to MDPV, mephedrone, and methylone would result in increased drug concentrations and enhanced total drug concentrations when compared to individual administration., Methods: Adolescent male Swiss-Webster mice were injected intraperitoneally with either 10 mg/kg MDPV, 10 mg/kg mephedrone, 10 mg/kg methylone, or 10 mg/kg combined MDPV, mephedrone, and methylone. Following injection, brains and plasma were collected at 1, 10, 15, 30, 60, and 120 min. Drugs were extracted via solid-phase extraction, and concentrations were determined using a previously published high-pressure liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method., Results: All drugs crossed the blood-brain barrier quickly. For methylone, the maximal concentration (C max ) and the total drug exposure [as represented by the area under the concentration-time curve (AUC)] were significantly higher when combined with mephedrone and MDPV in both matrices (2.89-fold increase for both C max and AUC with combined treatment). For mephedrone, the C max was unchanged, but the AUC in brain was increased when in combination by approximately 34%. Interestingly, for MDPV, the C max was unchanged, yet the AUC was higher when MDPV was administered individually (there was a 62% decrease in AUC with combined treatment)., Conclusions: The pharmacokinetics of methylone, mepedrone, and MDPV are altered when the drugs are used in combination. These data provide insight into the consequences of co-exposure to synthetic cathinones in popular bath salt products., (© 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background: Several disease states commonly associated with methamphetamine (METH) use produce liver dysfunction, and in the bile duct ligation (BDL) model of hepatic dysfunction, rats with liver injury are more sensitive to METH effects. Additionally, both female rats and humans are known to be more sensitive to METH than males. In consideration of known sex-dependent differences in METH pharmacokinetics, this study sought to determine the potential interaction between sex and liver dysfunction variables on METH pharmacokinetics., Methods: Sham or BDL surgery was performed on male and female rats on day 0. Serum biomarker and pharmacokinetics studies with 3 mg/kg subcutaneous (SC) METH were performed on day 7. METH-induced weight loss was measured on day 8. Liver histology evaluation and brain METH concentration measurements were performed on day 9., Results: While BDL surgery produced significantly elevated alanine aminotransferase and bile duct proliferation in male compared to female rats, there were no significant interactions between sex and liver function in the pharmacokinetic parameters. Both liver dysfunction and female sex, however, were associated with significantly slower METH serum clearance and significantly higher brain METH concentrations (p < .05)., Conclusions: BDL-induced hepatic dysfunction produces substantial reductions in METH clearance and increased brain METH concentrations in both male and female rats, despite less liver injury in females. This preclinical model may be useful to identify and correct potential liver dysfunction comorbidity-related problems with future pharmacotherapy for stimulant use disorder with METH prior to expensive clinical trials., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Methamphetamine (MA) is a highly addictive central nervous system stimulant. MA use disorder is characterized by a chronic, relapsing brain disease that is enhanced by a dynamic process of repeated use and withdrawal. The analysis of MA and its metabolite, amphetamine (AM), in hair is routinely performed in forensic laboratories for illegal MA use determination. However, few studies regarding the clinical application of hair analysis have been conducted to monitor the treatment of MA use disorder. Herein, the characteristics of Korean patients with MA use disorder were investigated based on drug abuse screening instruments and quantitative analysis of MA and AM in hair. A HPLC-MS/MS method for the quantification of MA and AM in hair was validated and clinically applied to healthy subjects (HS, n = 30, male) as well as current (CP, n = 33, male) and former (FP, n = 22, male) MA use disorder patients. The validation results of the hair analysis method showed high selectivity, accuracy, and precision with acceptable linearity within the calibration range (0.05-5.0 ng/mg). The limit of detection (LOD) and limit of quantification for both MA and AM were 0.05 ng/mg. The concentrations of MA and AM ranged from ≤ LOD to 166 ng/mg and from not detected (ND) to 9.15 ng/mg in the CP group and from ND to 6.14 ng/mg and from ND to 0.32 ng/mg in the FP group, respectively. No correlation was observed between the hair MA concentrations and the NIDA-modified ASSIST, DUDID extended, or DAST scores in both groups. The hair MA concentrations showed advantages for differentiating the CP and FP groups compared with the scores provided by the above-mentioned drug abuse screening instruments.

The effect of urine pH on renal excretion and systemic disposition has been observed for many drugs and metabolites. When urine pH is altered, tubular ionization, passive reabsorption, renal clearance, and systemic exposure of drugs and metabolites may all change dramatically, raising clinically significant concerns. Surprisingly, the urine pH effect on drug disposition is not routinely explored in humans, and regulatory agencies have neither developed guidance on this issue nor required industry to conduct pertinent human trials. In this study, we hypothesized that physiologically based pharmacokinetic (PBPK) modeling could be used as a cost-effective method to examine potential urine pH effect on drug and metabolite disposition. Our previously developed and verified mechanistic kidney model was integrated with a full-body PBPK model to simulate renal clearance and area under the plasma concentration-time curve (AUC) with varying urine pH statuses using methamphetamine and amphetamine as model compounds. We first developed and verified drug models for methamphetamine and amphetamine under normal urine pH condition [absolute average fold error (AAFE) < 1.25 at study level]. Then, acidic and alkaline urine scenarios were simulated. Our simulation results show that the renal excretion and plasma concentration-time profiles for methamphetamine and amphetamine could be recapitulated under different urine pH (AAFE < 2 at individual level). The methamphetamine-amphetamine parent-metabolite full-body PBPK model also successfully simulated amphetamine plasma concentration-time profiles (AAFE < 1.25 at study level) and amphetamine/methamphetamine urinary concentration ratios (AAFE < 2 at individual level) after dosing methamphetamine. This demonstrates that our mechanistic PBPK model can predict urine pH effect on systemic and urinary disposition of drugs and metabolites. SIGNIFICANCE STATEMENT: Our study shows that integrating mechanistic kidney model with full-body physiologically based pharmacokinetic model can predict the magnitude of alteration in renal excretion and area under the plasma concentration-time curve (AUC) of drugs and metabolites when urine pH is changed. This provides a cost-effective method to evaluate the likelihood of renal and systemic disposition changes due to varying urine pH. This is important because multiple drugs and diseases can alter urine pH, leading to quantitatively and clinically significant changes in drug and metabolite disposition that may require adjustment of therapy., (Copyright © 2020 by The American Society for Pharmacology and Experimental Therapeutics.)

Synthetic cathinones, such as methylone and pentedrone, are psychoactive derivatives of cathinone, sold in the internet as "plant food" or "bath salts". However, the level at which these compounds and their enantiomers cross the intestinal barrier has not been yet determined. Thus, the present study aimed to analyze the enantioselectivity on the permeability of these drugs through the intestinal barrier by using the Caco-2 cell line, a widely used in vitro model for drug permeability studies. To achieve this goal, an UHPLC-UV method was developed and validated to quantify both synthetic cathinones. The developed UHPLC-UV method revealed high selectivity and a linearity from 1 to 500 μM with correlation coefficients always higher than 0.999. The method has an accuracy that ranged between 89 and 107%, inter-day and intra-day precisions with coefficients of variation below 10%, limits of detection and quantification of 0.31 μM and 0.93 μM for methylone and 0.17 μM and 0.52 μM for pentedrone, respectively. In Caco-2 cells, a differentiated passage of the enantiomers across monolayer was observed for both cathinones. For pentedrone, the difference was observed after the first hour, being R-(-)-pentedrone the most permeable compound. Regarding methylone, the difference was noted after one hour and 30 min, with S-(-)-methylone being the most absorbed enantiomer. In conclusion, a fully validated method was successfully applied for studying the permeability of methylone and pentedrone enantiomers in an in vitro model of human intestine, which allowed to discover, for the first time, the enantioselectivity in drug permeability of this class of drugs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Methamphetamine (METH), an addictive stimulant of neurotransmitters, is associated with cardiovascular and neurological diseases. METH-induced ophthalmic complications are also present but have been insufficiently investigated. The purpose of this study is to investigate the retinal effects of METH. C57BL/6 mice were administrated progressively increasing doses of METH (0-6 mg/kg) by repetitive intraperitoneal injections for 5 days (4 times per day). Retinal degeneration was examined by morphological changes and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) assay. Norepinephrine levels were measured by ELISA, protein expression levels were determined by immunoblot and immunostaining, and gelatinase activity was examined by zymography. The thickness of the retina and the number of nuclei in the inner and outer nuclear layers were decreased by METH. Retinal cell death and astrocyte activation by METH treatment were confirmed by TUNEL assay and glial fibrillary acidic protein expression, respectively. Increased tumor necrosis factor-α protein in the retina and elevated norepinephrine levels in plasma were found in METH-treated mice. Platelet endothelial cell adhesion molecule-1 (PECAM-1) protein expression level was decreased in the retina and central retinal artery (CRA) by METH treatment, along with the endothelial proteoglycans glypican-1 and syndecan-1. Moreover, a regulator of the extracellular matrix, matrix metalloproteinase-14 (MMP-14) in the retina, and MMP-2 and MMP-9 in plasma, were increased by METH treatment. In conclusion, METH administration is involved in retinal degeneration with a vascular loss of PECAM-1 and the glycocalyx in the CRA and retina, and an increase of MMPs., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Methamphetamine use disorder continues to be inadequately treated, but improvements are being made in the field of immunotherapeutics, including vaccines, which could provide new options for treatment. Cocaine and nicotine vaccines have been tested clinically, but have yet to elicit the necessary antibody concentrations required to be effective. Methamphetamine vaccines have been tested in multiple nonclinical models and appear promising. Improved adjuvants have the potential to further stimulate the immune system to reach effective levels of antibodies. Previously, the methamphetamine vaccine IXT-v100 was administered with GLA-SE, a toll-like receptor 4 agonist, in mice to produce higher levels of antibodies than when it was administered with two other widely used adjuvants, Alhydrogel and Sigma Adjuvant System., Methods: The purpose of this research was to evaluate IXT-v100, given in combination with the adjuvant GLA-SE, to determine its efficacy in antagonizing methamphetamine disposition in a rat pharmacokinetic study. Additional rat studies were conducted to compare the ability of IXT-v100 manufactured with greater hapten densities to elicit higher antibody levels., Results: As expected based on prior studies with anti-methamphetamine monoclonal antibodies, the antibodies resulting from vaccination with IXT-v100 altered methamphetamine pharmacokinetics by increasing serum concentrations and extending the half-life. Furthermore, intentional variations in the ratio of components during manufacturing led to production of vaccines with higher hapten densities. The higher hapten densities resulted in production of antibodies that maintained the ability to bind methamphetamine with high affinity., Conclusions: The results support continued development of IXT-v100 for the treatment of methamphetamine use disorder., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Methamphetamine (MA) impairs vesicular monoamine transporter 2 (VMAT2) and dopamine transporter (DAT) function and expression, increasing intracellular DA levels that lead to neurotoxicity. The trace amine-associated receptor 1 (TAAR1) is activated by MA, but when the receptor is not activated, MA-induced neurotoxicity is increased. To investigate interactions among TAAR1, VMAT2, and DAT, transporter function and expression were measured in transgenic Taar1 knockout (KO) and wild-type (WT) mice 24 hours following a binge-like regimen (four intraperitoneal injections, 2 hours apart) of MA (5 mg/kg) or the same schedule of saline treatment. Striatal synaptosomes were separated by fractionation to examine the function and expression of VMAT2 localized to cytosolic and membrane-associated vesicles. DAT was measured in whole synaptosomes. VMAT2-mediated [ 3 H]DA uptake inhibition was increased in Taar1 KO mice in synaptosomal and vesicular fractions, but not the membrane-associated fraction, compared with Taar1 WT mice. There was no difference in [ 3 H]dihydrotetrabenazine binding to the VMAT2 or [ 125 I]RTI-55 binding to the DAT between genotypes, indicating activation of TAAR1 does not affect VMAT2 or DAT expression. There was also no difference between Taar1 WT and KO mice in DAT-mediated [ 3 H]DA uptake inhibition following in vitro treatment with MA. These findings provide the first evidence of a TAAR1-VMAT2 interaction, as activation of TAAR1 mitigated MA-induced impairment of VMAT2 function, independently of change in VMAT2 expression. Additionally, the interaction is localized to intracellular VMAT2 on cytosolic vesicles and did not affect expression or function of DAT in synaptosomes or VMAT2 at the plasmalemmal surface, i.e., on membrane-associated vesicles. SIGNIFICANCE STATEMENT: Methamphetamine stimulates the G protein-coupled receptor TAAR1 to affect dopaminergic function and neurotoxicity. Here we demonstrate that a functional TAAR1 protects a specific subcellular fraction of VMAT2, but not the dopamine transporter, from methamphetamine-induced effects, suggesting new directions in pharmacotherapeutic development for neurodegenerative disorders., (U.S. Government work not protected by U.S. copyright.)

Mephedrone (MEPH), the most widely consumed synthetic cathinone, has been associated with acute toxicity episodes. The aim of this report was to study its metabolic disposition and the impact of genetic variation of CYP2D6 on MEPH metabolism, in a dose range compatible with its recreational use. A randomized, crossover, phase I clinical trial was performed. Subjects received 50 and 100 mg (n = 3) and 150 and 200 mg (n = 6) of mephedrone and were genetically and phenotypically characterized for the CYP2D6 allelic variation. Our results showed a linear kinetics of mephedrone at the dose range assayed: plasma concentrations, cardiovascular and subjective effects, and blood serotonin concentrations all correlated in a dose-dependent manner. Mephedrone metabolic disposition is mediated by CYP2D6. Mephedrone pharmacology presented a linear dose-dependence within the range of doses tested. The metabolism of mephedrone by CYP2D6 implies that recreational users with no or low CYP2D6 functionality are exposed to unwanted acute toxicity episodes., (© 2019 The Authors Clinical Pharmacology & Therapeutics © 2019 American Society for Clinical Pharmacology and Therapeutics.)

Background: Chiral analysis is a crucial way to differentiate selegiline (SG) intake from drug abuse. Oral fluid (OF) has been successfully used as an alternative matrix for blood testing in several pharmacokinetic studies., Objective: The aim of this study is to describe the pharmacokinetics of SG and its main metabolites in OF after a single oral administration of SG which is meaningful for results interpretation in forensic analysis., Methods: Ten milligrams of SG were orally administered to 8 volunteers, and OF samples were collected for up to 96 hours by having participants spit into polypropylene tubes without stimulation. These samples were submitted to liquid-liquid extraction before analysis by liquid chromatography-tandem mass spectrometry operating in positive ion multiple-reaction monitoring mode., Results and Conclusions: After oral administration, each analyte could be detected in OF specimens from all volunteers with an initial detection time of 0.50 hours. The C max values of SG, R-MA, R-AM and DM-SG were 50.93-992.67 ng/mL, 29.78-653.64 ng/mL, 8.22-150.15 ng/mL, and 4.34-16.25 ng/mL, respectively, at 0.5 hours, 1-11 hours, 1.5-11 hours, and 0.5-6 hours post dose. The times when the compounds were last determined in OF were 5-24 hours for SG, 52-96 hours for R-MA, 31-96 hours for R-AM, and 13-31 hours for DM-SG after oral administration. There is a period of time in OF in which only MA and AM are present without SG and DM-SG after a single dose of SG. The pharmacokinetic data could provide supplementary interpretation for OF tests in forensic science and drug treatment programs., (© 2019 John Wiley & Sons, Ltd.)

Rationale: The synthetic cathinones are a class of designer drugs of abuse that share a common core scaffold. The pharmacokinetic profiles of the synthetic cathinones vary based on the substitutions to the core scaffold., Objectives: To provide a summary of the literature regarding the pharmacokinetic characteristics of the synthetic cathinones, with a focus on the impact of the structural modifications to the pharmacokinetics., Results: In many, but not all, instances the pharmacokinetic characteristics of the synthetic cathinones can be reasonably predicted based on the substitutions to the core scaffold. Mephedrone and methylone are chemically alike and have similar T max and t 1/2 in male rats. MDPV, a structurally distinct synthetic cathinone from mephedrone and methylone, has a lower T max and t 1/2 . Increasing the length of the alkyl chain on the α position of methylone, to produce pentylone, results in increased plasma concentrations and longer t 1/2 . Metabolism of the synthetic cathinones is reasonably predictable based on the chemical structure, and several phase I metabolites retain pharmacodynamic activity. CYP2D6 is implicated in the metabolism of all of the synthetic cathinones, and other P450s (CYP1A2, CYP2B6, and CYP2C19) are known to contribute variably to the metabolism of specific synthetic cathinones., Conclusions: Continued research will lead to a better understanding of the pharmacokinetic changes associated with structural modifications to the cathinone scaffold, and potentially in the long range, enhanced overdose and addiction therapy. Additionally, the areas of polydrug use and pharmacogenetics have been largely overlooked with regard to synthetic cathinones.

The abuse of drugs has become a serious social problem worldwide. Amphetamine-type stimulants such as methamphetamine are recreationally abused and can cause toxic effects in the body. Unfortunately, death from drug poisoning can occur due to careless intake. In postmortem examinations, the distribution of drugs in an entire organ gives valuable information for evaluating their toxicity. We developed methods to measure the distribution of drugs in organs using LC/MS and matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS). The complementary use of the two methods provides more detailed information on the distribution and concentration of drugs in organs because the accurate quantification in LC/MS and small spatial resolution in MALDI-IMS are combined. On the other hand, it is important to elucidate the drug intake history of suspects and victims in drug-facilitated crimes (DFCs). Hair and nail samples are often used to confirm chronic drug intake because ingested drugs can stably remain in these specimens over several months. However, it is impossible to determine the day of drug ingestion in conventional segmental analysis of bulk samples. Therefore, we developed methods to cut hair strands at 0.4-mm intervals and nails at 0.2-mm intervals, which correspond to their respective growth rates over 1-2 d, to analyze the drugs in each segment efficiently using LC/MS. The microsegmental hair analysis method is applied to estimate the day of drug ingestion in DFC investigations. These methods could be applied to measure the distribution of compounds in various solid samples.

Purpose: Methamphetamine (METH) abuse is associated with hepatic dysfunction related comorbidities such as HIV, hepatitis C, and polysubstance abuse with acetaminophen-containing opioid formulations. We aimed to develop a bile duct ligation (BDL)-induced hepatic dysfunction model for studying both METH and experimental treatments for METH abuse in this comorbidity., Methods: Sham or BDL surgery was performed in male Wistar rats on day 0. Liver function was measured throughout the study. On days 7 and 19, serum pharmacokinetics studies were performed with 1 mg/kg subcutaneous (sc) METH. On day 21, this dose was repeated to determine 2 h post-METH brain concentrations. METH-induced open field behaviors were measured every other day (days 12 - 16) with ascending sc doses (0.3 - 3 mg/kg)., Results: BDL transiently increased alanine aminotransferase levels and altered liver structure, which resulted in significantly greater METH serum and brain exposure. In the BDL compared to sham group, there was a longer duration of METH-induced locomotor activity (after 1 and 3 mg/kg) and stereotypy (after 3 mg/kg)., Conclusions: In rats, liver dysfunction reduced METH clearance, increased brain METH concentrations, and enhanced METH effects on locomotor activity in a dose dependent manner. In addition, this model could be further developed to simulate the associated hepatic dysfunction of key METH abuse comorbidities for preclinical testing of novel pharmacotherapies for effectiveness and/or toxicity in vulnerable populations.

1. Methylone (3,4-methylenedioxy-N-methylcathinone, MDMC), which appeared on the illicit drug market in 2004, is a frequently abused synthetic cathinone derivative. Known metabolic pathways of MDMC include N-demethylation to normethylone (3,4-methylenedioxycathinone, MDC), aliphatic chain hydroxylation and oxidative demethylenation followed by monomethylation and conjugation with glucuronic acid and/or sulphate. 2. Three new phase II metabolites, amidic conjugates of MDC with succinic, glutaric and adipic acid, were identified in the urine of rats dosed subcutaneously with MDMC.HCl (20 mg/kg body weight) by LC-ESI-HRMS using synthetic reference standards to support identification. 3. The main portion of administered MDMC was excreted unchanged. Normethylone, was a major urinary metabolite, of which a minor part was conjugated with dicarboxylic acids. 4. Previously identified ring-opened metabolites 4-hydroxy-3-methoxymethcathinone (4-OH-3-MeO-MC), 3-hydroxy-4-methoxymeth-cathinone (3-OH-4-MeO-MC) and 3,4-dihydroxymethcathinone (3,4-di-OH-MC) mostly in conjugated form with glucuronic and/or sulphuric acids were also detected. 5. Also, ring-opened metabolites derived from MDC, namely, 4-hydroxy-3-methoxycathinone (4-OH-3-MeO-C), 3-hydroxy-4-methoxycathinone (3-OH-4-MeO-C) and 3,4-dihydroxycathinone (3,4-di-OH-C) were identified for the first time in vivo.

Mephedrone is a synthetic cathinone consumed as a recreational drug. Recently, it was identified several of its metabolites in vivo in humans but there is little information about its pharmacokinetics in plasma and urine. Although several analytical methods have been proposed for mephedrone quantification in different matrices, none are available for its metabolites. Therefore, the aim of the study was to develop and validate an analytical method using liquid chromatography-tandem mass spectrometry for the quantification of mephedrone, nor-mephedrone, N-succinyl-nor-mephedrone, 1'-dihydro-mephedrone, and 4'-carboxy-mephedrone. The method was validated in human plasma and urine and in rat brain homogenates. Six healthy male subjects, recreational users of new psychoactive substances, ingested 150 mg of mephedrone within the context of a clinical trial. 4'-Carboxy-mephedrone, followed by nor-mephedrone, was the most abundant metabolites found in plasma. Dihydro-mephedrone represented 10% of the amount of mephedrone in plasma and N-succinyl-nor-mephedrone was the metabolite eliminated with the longer half-life of 8.2 h. In urine, 4'-carboxy-mephedrone was the main metabolite excreted with amounts recovered being about 10 times those of mephedrone. Additionally, the validated method was used to test metabolite ability to cross the blood-brain barrier in vivo in rats with mephedrone and nor-mephedrone as the main active compounds present in the brain. The method described is useful for the determinations of mephedrone and metabolites in biological samples. Graphical Abstract ᅟ.

Chronic methamphetamine (METH) abuse has been shown to elicit strong neurotoxic effects. Yet, with an increasing number of children born to METH abusing mothers maturing into adulthood, one important question is how far do the neurotoxic effects of METH alter various neurotransmitter systems in the adult METH-exposed offspring. The purpose of this study was to investigate long-term trans-generational neurochemical changes, following prenatal METH exposure, in the adult Wistar rat brain. METH or saline (SAL-control animals) was administered to pregnant dams throughout the entire gestation period (G0-G22). At postnatal day 90, dopamine, serotonin, glutamate and GABA were measured in the adult brain before (baseline) and after a METH re-administration using in vivo microdialysis and liquid chromatography/mass spectrometry. The results show that METH-exposure increased basal levels of monoamines and glutamate, but decreased GABA levels in all measured brain regions. Acute challenge with METH injection in the METH-exposed group induced a lower increase in the monoamine system relative to the increase in the GABAergic and glutamatergic system. The data show that prenatal METH exposure has strong effects on the monoaminergic, GABAergic and glutamatergic system even when exposure to METH was limited to the prenatal phase. Toxicological effects of METH have therefore longer lasting effects as currently considered and seem to affect the excitatory-inhibitory balance in the brain having strong implications for cognitive and behavioral functioning.

Medico-legal experts are increasingly enlisted to assess the methamphetamine and amphetamine serum concentrations after a criminal offense. However, since criminal users rarely provide useful information to medico-legal experts regarding the substances abused, when the substance(s) was/were used, dose of ingestion tools are needed to interpret the analytical data, which can be used as objective evidence in such cases. A comparative series of methamphetamine and amphetamine serum concentrations were used to analyze the frequency of concentrations, to determine methamphetamine/amphetamine concentration ratios, and prove them as a tool to distinguish pure methamphetamine from mixed amphetamine/methamphetamine ingestion. Additionally, two cases of survived accidental methamphetamine intoxication, resulting from ingestion smuggling which was longitudinally monitored, and pharmacokinetic parameters were assessed. In a series of 628 samples where the most frequent concentration of methamphetamine exceeded the therapeutic level, there was a strong correlation suggesting pure methamphetamine consumption, when the ratios of methamphetamine/amphetamine concentrations were within the range between 3 and 10. In the two cases of methamphetamine bodypacking, the relevant serum concentrations of methamphetamine and amphetamine, which could be measured up to 9 days after ingestion, indicated a decrease of the methamphetamine/amphetamine ratios in an exponential manner. However, the ratios were not always within the range between 3 and 10. Lastly, the course of the serum concentrations suggested an increase of the apparent elimination half-life of methamphetamine. In terms of the objective evidence required in criminal law, calculating methamphetamine/amphetamine concentration ratio is not a suitable to means to distinguish pure methamphetamine intake and that of mixed amphetamine/methamphetamine abuse in an individual case. Instead, methamphetamine high serum concentrations and the possible increase in apparent elimination half-life suggest that an extended detection period may be used to distinguish between "illicit use" as compared to "therapeutic use" of methamphetamine.

In recent years, the abuse of synthetic cathinones or 'bath salts' has become a major public health concern. Although these compounds were initially sold legally and labeled "not for human consumption", the 'bath salts' are psychostimulants, with similar structures and pharmacologic mechanisms to cocaine, the amphetamines, and 3,4 methylendioxymethamphetamine (MDMA, Molly, or Ecstasy). The reported use of these substances by women of child-bearing age highlights the necessity of studies seeking to delineate risks of prenatal exposure. Three popular drugs of this type are methylone, mephedrone, and 3, 4-methylenedioxypyrovalerone (MDPV). Unfortunately, there is currently no information available on the teratogenicity of these compounds, or of the extent to which they cross the placenta. As such, the purpose of this study was to examine the pharmacokinetic profile of the 'bath salts' in a pregnancy model. Pregnant mice (E17.5 gestation) were injected intraperitoneally with a cocktail of 5mg/kg methylone, 10mg/kg mephedrone, and 3mg/kg (MDPV) dissolved in sterile saline. Maternal brain, maternal plasma, placenta, and fetal brain were collected at 30s, 1min, 5min, 10min, 15min, 30min, 1h, 2h, 4h, and 8h following injection. Methylone, mephedrone, and MDPV were extracted from tissue by solid phase extraction, and concentrations were determined using a previously validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Interestingly, all 3 cathinones reached measurable concentrations in the placenta, as well as the fetal brain; in fact, for MDPV, the maximal concentration (Cmax) was highest in fetal brain, while mephedrone's highest Cmax value was achieved in placenta. Additionally, the total drug exposure for all 3 compounds (as represented by area under the curve, AUC) was higher in fetal matrices (placenta and fetal brain) than in maternal matrices (maternal brain and plasma), and the half-lives for the drugs were longer. Given the extensive presence of methylone, mephedrone, and MDPV in the fetal brain following prenatal exposure, fetal risk is definitely a concern. As there are currently no prenatal studies available on the teratogenicity of these agents, pregnant patients should be informed about the potential risks that these substances may have., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Drug abuse (e.g., methamphetamine-Meth or cocaine-Coc) is one of the major risk factors for becoming infected with HIV-1, and studies show that in combination, drug abuse and HIV-1 lead to significantly greater damage to CNS. To overcome these issues, we have developed a novel nanoformulation (NF) for drug-abusing population infected with HIV-1. In this work, a novel approach was developed for the co-encapsulation of Nelfinavir (Nel) and Rimcazole (Rico) using layer-by-layer (LbL) assembled magnetic nanoformulation for the cure of neuroAIDS. Developed NF was evaluated for blood-brain barrier (BBB) transmigration, cell uptake, cytotoxicity and efficacy (p24 assay) in HIV-1 infected primary astrocyte (HA) in presence or absence of Coc and Meth. Developed magnetic nanoformulation (NF) fabricated using the LbL approach exhibited higher amounts of drug loading (Nel and Rico) with 100% release of both the therapeutic agents in a sustained manner for 8 days. NF efficacy studies indicated a dose-dependent decrease in p24 levels in HIV-1-infected HA (~55%) compared to Coc + Meth treated (~50%). The results showed that Rico significantly subdued the effect of drugs of abuse on HIV infectivity. NF successfully transmigrated (38.8 ± 6.5%) across in vitro BBB model on the application of an external magnetic field and showed >90% of cell viability with efficient cell uptake. In conclusion, our proof of concept study revealed that sustained and concurrent release of sigma σ1 antagonist and anti-HIV drug from the developed novel sustained release NF can overcome the exacerbated effects of drugs of abuse in HIV infection and may solve the issue of medication adherence in the drug-abusing HIV-1 infected population.

l-Methamphetamine has been occasionally referred to as a stimulant similar to d-methamphetamine, probably owing to insufficient comparative studies. Here, we directly compared psychomotor efficacies and pharmacokinetics of methamphetamine enantiomers in mice. Only d-methamphetamine, but not l-methamphetamine, induced stereotypy and sensitization at 1-10 mg/kg. However, plasma pharmacokinetic parameters of 10 mg/kg l-methamphetamine were ≥tenfold those of 1 mg/kg d-methamphetamine. These results clearly indicate that differential psychomotor efficacies of methamphetamine enantiomers are independent of their pharmacokinetic profiles.

Benzphetamine is a Schedule III anorectic agent that is a prodrug for d-amphetamine and d-methamphetamine and may have utility as an "agonist" medication for cocaine use disorder treatment. This study evaluated the pharmacokinetic-pharmacodynamic profile of benzphetamine using a drug discrimination procedure in rhesus monkeys. The potency and time course of cocaine-like discriminative stimulus effects were compared for benzphetamine (10-18mg/kg, intramuscular (IM)) and d-amphetamine (0.032-0.32mg/kg, IM) in monkeys (n=3-4) trained to discriminate IM cocaine (0.32mg/kg) from saline in a two-key food-reinforced discrimination procedure. Parallel pharmacokinetic studies in the same monkeys determined plasma benzphetamine, d-methamphetamine and/or d-amphetamine levels for correlation with behavioral effects. d-Amphetamine produced dose-dependent, time-dependent, and full cocaine-like effects, i.e. ≥90% cocaine-appropriate responding, in all monkeys without altering response rates. The time course of d-amphetamine's cocaine-like discriminative stimulus effects correlated with plasma d-amphetamine levels. Benzphetamine was 180-fold less potent than d-amphetamine and produced full cocaine-like effects in only 2 of 4 monkeys while significantly decreasing response rates. Benzphetamine administration increased plasma d-methamphetamine (peak at 100min) and d-amphetamine (peak at 24h) levels, but the time course of behavioral effects did not correlate with increased levels of benzphetamine, d-methamphetamine or d-amphetamine. These results suggest that benzphetamine yields d-amphetamine and d-methamphetamine as active metabolites in rhesus monkeys, but generation of these metabolites is not sufficient to account for benzphetamine behavioral effects. The incomplete cocaine substitution profile and protracted d-amphetamine plasma levels suggest that benzphetamine may still warrant further evaluation as a candidate pharmacotherapy for cocaine use disorder treatment., (Copyright © 2017 Elsevier Inc. All rights reserved.)

3,4-Methylenedioxy-N-methylcathinone (methylone) is a new psychoactive substance and the β-keto analog of 3,4-methylenedioxy-N-methylamphetamine (MDMA). It is well established that MDMA metabolism produces bioactive metabolites. Here we tested the hypothesis that methylone metabolism in rats can form bioactive metabolites. First, we examined the pharmacokinetics (PKs) of methylone and its metabolites after subcutaneous (sc) methylone administration (3, 6, 12 mg/kg) to male rats fitted with intravenous (iv) catheters for repeated blood sampling. Plasma specimens were assayed by liquid chromatography tandem mass spectrometry to quantify methylone and its phase I metabolites: 3,4-methylenedioxycathinone (MDC), 3,4-dihydroxy-N-methylcathinone (HHMC), and 4-hydroxy-3-methoxy-N-methylcathinone (HMMC). The biological activity of methylone and its metabolites was then compared using in vitro transporter assays and in vivo microdialysis in rat nucleus accumbens. For the PK study, we found that methylone and MDC peaked early (T max =15-45 min) and were short lived (t 1/2 =60-90 min), while HHMC and HMMC peaked later (T max =60-120 min) and persisted (t 1/2 =120-180 min). Area-under-the-curve values for methylone and MDC were greater than dose-proportional, suggesting non-linear accumulation. Methylone produced significant locomotor activation, which was correlated with plasma methylone, MDC, and HHMC concentrations. Methylone, MDC, and HHMC were substrate-type releasers at monoamine transporters as determined in vitro, but only methylone and MDC (1, 3 mg/kg, iv) produced significant elevations in brain extracellular dopamine and 5-HT in vivo. Our findings demonstrate that methylone is extensively metabolized in rats, but MDC is the only centrally active metabolite that could contribute to overall effects of the drug in vivo.

Background: Methamphetamine dependence is a significant public health concern without any approved medications for treatment. We evaluated ibudilast, a nonselective phosphodiesterase inhibitor, to assess the safety and tolerability during intravenous methamphetamine administration. We conducted a randomized, double-blind, placebo-controlled, within-subjects crossover clinical trial., Methods: Participants received ibudilast (20 mg twice daily followed by 50 mg twice daily) and placebo, with order determined by randomization, and then underwent intravenous methamphetamine challenges (15 and 30 mg). We monitored cardiovascular effects, methamphetamine pharmacokinetics, and reported adverse events., Results: Ibudilast treatment had similar rates of adverse events compared with placebo, and there was no significant augmentation of cardiovascular effects of methamphetamine. Pharmacokinetic analysis revealed no clinically significant change in maximum concentration or half-life of methamphetamine with ibudilast., Conclusions: Methamphetamine administration during ibudilast treatment was well tolerated without additive cardiovascular effects or serious adverse events, providing initial safety data to pursue ibudilast's effectiveness for the treatment of methamphetamine dependence.

Occupants of former methamphetamine laboratories, often residences, may experience increased exposure through the accumulation of the methamphetamine in the organic films that coat skin and indoor surfaces. The objectives of this study were to determine equilibrium partition coefficients of vapor-phase methamphetamine with artificial sebum (AS-1), artificial sebum without fatty acids (AS-2), and real skin surface films, herein called skin oils. Sebum and skin oil-coated filters were exposed to vapor-phase methamphetamine at concentrations ranging from 8 to 159 ppb, and samples were analyzed for exposure time periods from 2 h to 60 days. For a low vapor-phase methamphetamine concentration range of ~8-22 ppb, the equilibrium partition coefficient for AS-1 was 1500 ± 195 μg/g/ppb. For a high concentration range of 98-112 ppb, the partition coefficient was lower, 459 ± 80 μg/g/ppb, suggesting saturation of the available absorption capacity. The low partition coefficient for AS-2 (33 ± 6 μg/g/ppb) suggests that the fatty acids in AS-1 and skin oil are responsible for much high partition coefficients. We predict that the methamphetamine concentration in skin lipids coating indoor surfaces can exceed recommended surface remediation standards even for air concentrations well below 1 ppb., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Addiction to psychostimulants is a major public health problem with no available treatment. Adenosine A2A receptors (A2A R) co-localize with metabotropic glutamate 5 receptors (mGlu5 R) in the striatum and functionally interact to modulate behaviours induced by addictive substances, such as alcohol. Using genetic and pharmacological antagonism of A2A R in mice, we investigated whether A2A R-mGlu5 R interaction can regulate the locomotor, stereotypic and drug-seeking effect of methamphetamine and cocaine, two drugs that exhibit distinct mechanism of action. Genetic deletion of A2A R, as well as combined administration of sub-threshold doses of the selective A2A R antagonist (SCH 58261, 0.01 mg/kg, i.p.) with the mGlu5 R antagonist, 3-((2-methyl-4-thiazolyl)ethynyl)pyridine (0.01 mg/kg, i.p.), prevented methamphetamine- but not cocaine-induced hyperactivity and stereotypic rearing behaviour. This drug combination also prevented methamphetamine-rewarding effects in a conditioned-place preference paradigm. Moreover, mGlu5 R binding was reduced in the nucleus accumbens core of A2A R knockout (KO) mice supporting an interaction between these receptors in a brain region crucial in mediating addiction processes. Chronic methamphetamine, but not cocaine administration, resulted in a significant increase in striatal mGlu5 R binding in wild-type mice, which was absent in the A2A R KO mice. These data are in support of a critical role of striatal A2A R-mGlu5 R functional interaction in mediating the ambulatory, stereotypic and reinforcing effects of methamphetamine but not cocaine-induced hyperlocomotion or stereotypy. The present study highlights a distinct and selective mechanistic role for this receptor interaction in regulating methamphetamine-induced behaviours and suggests that combined antagonism of A2A R and mGlu5 R may represent a novel therapy for methamphetamine addiction., (© 2015 Society for the Study of Addiction.)

Background: Methamphetamine (MA) use by pregnant women remains a growing problem in South East Asia. After delivery, a negative maternal urine MA assay is assumed to reflect the absence of MA in breast milk and marks breastfeeding initiation. To date, no data exist that describe the relationship between the peripartum and postpartum transfer of MA into breast milk and its urinary excretion in women, following recreational use by smoking., Objective: This study aimed to determine the pharmacokinetic of smoked MA in breast milk and its relationship to urinary MA excretion in postpartum women who tested positive for MA before delivery., Methods: Timed urine and breast milk samples of 33 women who had positive urine drug screens for MA prior to delivery were analyzed for MA using Acquity Ultra Performance Liquid Chromatography (Waters, Milford, Massachusetts, USA) with the ACQUITY UPLC Photodiode Array Detector (Waters). Those participants with 4 or more timed breast milk samples were included for pharmacokinetic calculation using log-linear trapezoidal rule., Results: Pharmacokinetic data from 2 women were analyzed. The half-life values for MA in the breast milk were 11.3 and 40.3 hours. The absolute infant doses were 21.3 and 51.7 µg/kg/day. Methamphetamine disappears from breast milk approximately 1 day before the maternal urine MA becomes negative., Conclusion: Smoked MA shows a similar breast milk pharmacokinetic pattern to previously reported intravenous MA. Breastfeeding can be safely initiated in mothers whose urine MA screen has turned negative for ≥ 24 hours. However, concurrent maternal substance use treatment and screening is necessary for continued promotion of lactation., (© The Author(s) 2015.)

In 2010-2013, 29 fatal intoxications related to the designer drug paramethoxymethamphetamine (PMMA, 4-methoxymethamphetamine) occurred in Norway. The current knowledge about metabolism and toxicity of PMMA in humans is limited. Metabolism by the polymorphic cytochrome P450 (CYP) 2D6 enzyme to the psychoactive metabolite 4-hydroxymethamphetamine (OH-MA), and possibly by additional enzymes, is suggested to be involved in its toxicity. The aim of this work was to study the association between CYP genetics, PMMA metabolism and risk of fatal PMMA toxicity in humans. The frequency distribution of clinically relevant gene variants of CYP2D6, CYP2C9, CYP2C19 and CYP3A5, and the phenotypic blood CYP2D6 metabolic ratio (OH-MA/PMMA) in particular, were compared in fatal PMMA intoxications (n=17) and nonfatal PMMA abuse controls (n=30), using non-abusers (n=305) as references for the expected genotype frequencies in the Norwegian population. Our study demonstrated that the CYP2D6 enzyme and genotype are important in the metabolism of PMMA to OH-MA in humans, but that other enzymes are also involved in this biotransformation. In the fatal PMMA intoxications, the blood concentrations of PMMA were higher and the CYP2D6 metabolic ratios were lower, than in the nonfatal PMMA abuse controls (median (range) 2.1 (0.03-5.0) vs 0.3 (0.1-0.9) mg/L, and ratio 0.6 (0.0-4.6) vs 2.1 (0.2-7.4) p=0.021, respectively). Overall, our findings indicated that, in most cases, PMMA death occurred rapidly and at an early stage of PMMA metabolism, following the ingestion of large and toxic PMMA doses. We could not identify any genetic CYP2D6, CYP2C9, CYP2C19 or CYP3A5 predictive marker on fatal toxicity of PMMA in humans. The overrepresentation of the CYP2D6 poor metabolizer (PM) genotype found in the nonfatal PMMA abuse controls warrants further investigations., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

In this study, methamphetamine (Meth)- and glutamate (Glu)-mediated intracellular Ca(++) (Ca(++) i) signals were examined in real time in primary cortical neurons overexpressing an intracellular Ca(++) probe, GCaMP5, by adeno-associated viral (AAV) serotype 1. Binding of Ca(++) to GCaMP increased green fluorescence intensity in cells. Both Meth and Glu induced a rapid increase in Ca(++) i, which was blocked by MK801, suggesting that Meth enhanced Ca(++) i through Glu receptor in neurons. The Meth-mediated Ca(++) signal was also blocked by Mg(++) , low Ca(++) or the L-type Ca(++) channel inhibitor nifedipine. The ryanodine receptor inhibitor dantrolene did not alter the initial Ca(++) influx but partially reduced the peak of Ca(++) i. These data suggest that Meth enhanced Ca(++) influx through membrane Ca(++) channels, which then triggered the release of Ca(++) from the endoplasmic reticulum in the cytosol. AAV-GCaMP5 was also injected to the parietal cortex of adult rats. Administration of Meth enhanced fluorescence in the ipsilateral cortex. Using immunohistochemistry, Meth-induced green fluorescence was found in the NeuN-containing cells in the cortex, suggesting that Meth increased Ca(++) in neurons in vivo. In conclusion, we have used in vitro and in vivo techniques to demonstrate a rapid increase of Ca(++) i by Meth in cortical neurons through overexpression of GCaMP5. As Meth induces behavioral responses and neurotoxicity through Ca(++) i, modulation of Ca(++) i may be useful to reduce Meth-related reactions., (© 2014 Society for the Study of Addiction.)

Background: Amphetamine and methamphetamine are popular drugs of abuse worldwide and are important components of drug monitoring programs. Windows of detection for amphetamine and methamphetamine in oral fluid after high doses have not been investigated. Repeated high-dose ingestions are likely to cause positive samples for extended periods. Common routes of administration of amphetamine/methamphetamine in Norway are oral intake or injection. The aim of this study was to investigate windows of detection for amphetamine and methamphetamine in oral fluid from drug addicts under sustained abstinence during detoxification., Methods: Twenty-five patients admitted to a closed detoxification unit were included in this study. Oral fluid samples were collected daily in the morning and evening, and urine every morning for 10 days. A blood sample was drawn during the first 5 days after admission if the patient consented. Oral fluid results were compared with urine results to determine whether a new ingestion occurred. Oral fluid was collected with the Intercept oral fluid collection device. In-house cutoff concentrations for amphetamine and methamphetamine were 6.8 and 7.5 mcg/L, respectively, in oral fluid, and 135 and 149 mcg/L, respectively, in urine., Results: Amphetamines were detected in 11 oral fluid, 5 urine, and 2 blood specimens from 25 patients. Patients self-reported amphetamines intake of up to 0.5-2 g daily. Windows of detection for amphetamine and methamphetamine in oral fluid were up to 8 days, longer than in urine at the applied cutoff values., Conclusions: These data confirm that oral fluid is a viable alternative to urine for monitoring amphetamine abuse, and that these substances might be detected in oral fluid for at least 1 week after ingestion of high doses. Such long detection times were, as far as we are aware, never reported previously for oral fluid amphetamines.

Repeated methamphetamine (METH) administrations cause persistent dopaminergic deficits resembling aspects of Parkinson's disease. Many METH abusers smoke cigarettes and thus self-administer nicotine; yet few studies have investigated the effects of nicotine on METH-induced dopaminergic deficits. This interaction is of interest because preclinical studies demonstrate that nicotine can be neuroprotective, perhaps owing to effects involving α4β2 and α6β2 nicotinic acetylcholine receptors (nAChRs). This study revealed that oral nicotine exposure beginning in adolescence [postnatal day (PND) 40] through adulthood [PND 96] attenuated METH-induced striatal dopaminergic deficits when METH was administered at PND 89. This protection did not appear to be due to nicotine-induced alterations in METH pharmacokinetics. Short-term (i.e., 21-day) high-dose nicotine exposure also protected when administered from PND 40 to PND 61 (with METH at PND 54), but this protective effect did not persist. Short-term (i.e., 21-day) high-dose nicotine exposure did not protect when administered postadolescence (i.e., beginning at PND 61, with METH at PND 75). However, protection was engendered if the duration of nicotine exposure was extended to 39 days (with METH at PND 93). Autoradiographic analysis revealed that nicotine increased striatal α4β2 expression, as assessed using [(125)I]epibatidine. Both METH and nicotine decreased striatal α6β2 expression, as assessed using [(125)I]α-conotoxin MII. These findings indicate that nicotine protects against METH-induced striatal dopaminergic deficits, perhaps by affecting α4β2 and/or α6β2 expression, and that both age of onset and duration of nicotine exposure affect this protection., (Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.)

Background and Objectives: We previously reported that an anti-methamphetamine (MA) vaccine attenuated drug-conditioned effects in mice, but it used a carrier protein and adjuvant not available for clinical use. Here we produced a vaccine with the same hapten (succinyl-methamphetamine, SMA) but attached to tetanus toxoid (SMA-TT) and adsorbed to aluminum hydroxide, components approved for use in humans. We then assessed the vaccine's ability to generate anti-MA antibodies, alter acquisition and reinstatement of MA place conditioning, and prevent MA brain penetration., Methods: Mice were administered SMA-TT at weeks 0 and 3 and non-vaccinated mice received saline. Anti-MA antibody concentrations were determined at 8 and 12 weeks. Place conditioning began during week 9 in which vaccinated and non-vaccinated mice were divided into groups and conditioned with .5, or 2.0 mg/kg MA. Following acquisition training, mice were extinguished and then a reinstatement test was performed in which mice were administered their original training dose of MA. Separate groups of non-vaccinated and vaccinated mice were administered .5 and 2.0 mg/kg MA and brain MA levels determined., Results and Conclusions: Anti-MA antibody levels were elevated at week 8 and remained so through week 12. The SMA-TT vaccine attenuated acquisition and reinstatement of MA place conditioning. Significantly greater proportions of vaccinated mice during acquisition and reinstatement tests showed conditioned place aversion. Moreover, MA brain levels were decreased in vaccinated mice following administration of both doses of MA., Scientific Significance: Results support further development of anti-MA vaccines using components approved for use in humans., (© American Academy of Addiction Psychiatry.)

Purpose of Review: As the most popular psychostimulant in the world, methamphetamine use has reached epidemic proportions. Its enormous popularity has created subcultures of methamphetamine users all over the globe. The purpose of this review is to describe the geographic availability of different types of methamphetamine, the characteristics of each user population, and the psychosocial impact the two have on society., Recent Findings: Methamphetamine has diversified immensely from the early days of its use. Different forms of methamphetamine - ICE, powder, and pills - have different pharmacokinetic characteristics that make them popular among certain types of users. New studies have shown that addiction to methamphetamine results in a very characteristic loss of inhibition that augments various risk-taking behaviors in its users. Also, recent seizure data suggest that its production and trafficking is spreading into new areas of the globe., Summary: From recreational use to addiction, methamphetamine use represents a serious risk to health and wellbeing of the community. Recognizing the pattern of abuse in specific populations is the key to assessing the risk, implementing prevention, and harm reduction measures, as well as making public policies.

3-Methyl-methcathinone (3-MMC) is a novel, synthetic cathinone analog, recently linked to poisoning events among recreational users. The lack of pharmacological data on 3-MMC, prompted us to explore its pharmacokinetic profile as well as its effect on feeding behavior, weight gain, and serum biochemistry. 3-MMC was administered to male pigs (n=3, three months old) as a single intravenous dose (0.3 mg/kg), followed by a multiple oral dose administration (3 mg/kg) for five days and plasma and tissue concentrations determined. Concomitantly a control group consisting of two healthy male pigs received saline solution instead of 3-MMC according to the same administration schedule. 3-MMC effects on complete blood count, biochemistry, feed intake, and body weight were examined. The pigs were sacrificed and submitted to a pathological and histopathological examination. 3-MMC displayed rapid absorption with a peak concentration achieved within 5-10 min after oral ingestion and a plasma half-life of 0.8 h. The bioavailability was about 7%. 3-MMC tissue levels were below detectable levels 24 h after the last oral dosage. No treatment-related clinical signs were observed and no histopathological findings were detected. 3-MMC caused significant change in daily feed intake and weight gain over time. The animals treated with 3-MMC displayed a lower rate of increase in mean body weight. Caution needs to be practiced in terms of extrapolating the present data to human safety, due to the low sample size, low dosage, and the relatively short study duration as well as the lack of data on abuse potential of 3-MMC., (© The Author(s) 2015.)

Experimental Data: Orexinergic neurotransmission is involved in mediating temperature responses to methamphetamine (Meth). In experiments in rats, SB-334867 (SB), an antagonist of orexin receptors (OX1R), at a dose of 10 mg/kg decreases late temperature responses (t > 60 min) to an intermediate dose of Meth (5 mg/kg). A higher dose of SB (30 mg/kg) attenuates temperature responses to low dose (1 mg/kg) of Meth and to stress. In contrast, it significantly exaggerates early responses (t < 60 min) to intermediate and high doses (5 and 10 mg/kg) of Meth. As pretreatment with SB also inhibits temperature response to the stress of injection, traditional statistical analysis of temperature responses is difficult., Mathematical Modeling: We have developed a mathematical model that explains the complexity of temperature responses to Meth as the interplay between excitatory and inhibitory nodes. We have extended the developed model to include the stress of manipulations and the effects of SB. Stress is synergistic with Meth on the action on excitatory node. Orexin receptors mediate an activation of on both excitatory and inhibitory nodes by low doses of Meth, but not on the node activated by high doses (HD). Exaggeration of early responses to high doses of Meth involves disinhibition: low dose of SB decreases tonic inhibition of HD and lowers the activation threshold, while the higher dose suppresses the inhibitory component. Using a modeling approach to data assimilation appears efficient in separating individual components of complex response with statistical analysis unachievable by traditional data processing methods.

Background: Because methamphetamine (METH) pharmacokinetics after single iv doses show significant differences between male and female rats, we hypothesized that pharmacokinetic differences in METH disposition could be a contributing factor to the patterns of METH self-administration behaviors in rats., Methods: For the studies, we used a passive (non-contingent) METH dosing schedule consisting of 27 METH iv bolus injections (0.048mg/kg) over 2h derived from a previous active (contingent) METH self-administration behavioral study in male rats. After METH dosing of male and female Sprague-Dawley rats (n=5/group), METH and amphetamine serum concentrations were determined by LC-MS/MS. Pharmacokinetic analysis, including predictive mathematical simulations of the data, was then conducted., Results: Male and female rats achieved relatively stable METH serum concentrations within 20min, which remained constant from 20 to 120min. While not statistically different, METH clearance and volume of distribution values for females were 25% and 33% lower (respectively) than males. Linear regression analysis of predicted METH concentrations from pharmacokinetic simulations versus observed concentrations showed a substantially better correlation with male data than female data (r(2)=0.71 vs. 0.56; slope=0.95 vs. 0.45, respectively). At 120min, the time of predicted peak METH serum concentrations, female values were 42% higher than expected, while male values were within 3%., Conclusions: Unlike METH male pharmacokinetic data, the female data was less predictable during multiple METH administrations and produced overall higher than expected METH concentrations. These findings demonstrate that METH pharmacokinetics could contribute to differences in METH self-administration behaviors in rats., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Background: Methamphetamine is a highly addictive psychostimulant and the medical, social, and economic consequences associated with its use have become a major international problem. Current evidence has shown methamphetamine to be particularly neurotoxic to dopamine neurons and striatal structures within the basal ganglia. A previous study from our laboratory demonstrated larger putamen volumes in actively using methamphetamine-dependent participants. The purpose of this current study was to determine whether striatal structures in the same sample of participants also exhibit pathology on the microstructural and molecular level., Methods: Diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) were carried out in current methamphetamine users (n = 18) and healthy controls (n = 22) to investigate diffusion indices and neurometabolite levels in the basal ganglia., Results: Contrary to findings from previous DTI and MRS studies, no significant differences in diffusion indices or metabolite levels were observed in the basal ganglia regions of current methamphetamine users., Conclusions: These findings differ from those reported in abstinent users and the absence of diffusion and neurochemical abnormalities may suggest that striatal enlargement in current methamphetamine use may be due to mechanisms other than edema and glial proliferation., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Background: Despite initial reports of a decline in use in the early 2000s, methamphetamine remains a significant public health concern with known neurotoxic and neurocognitive effects to the user. The goal of this review is to update the literature on methamphetamine use and addiction since its assent to peak popularity in 1990s., Methods: We first review recent epidemiological reports with a focus on methamphetamine accessibility, changes in use and disorder prevalence rates over time, and accurate estimates of the associated burden of care to the individual and society. Second, we review methamphetamine pharmacology literature with emphasis on the structural and functional neurotoxic effects associated with repeated use of the drug. Third, we briefly outline the findings on methamphetamine-related neurocognitive deficits as assessed via behavioral and neuroimaging paradigms. Lastly, we review the clinical presentation of methamphetamine addiction and the evidence supporting the available psychosocial and pharmacological treatments within the context of an addiction biology framework., Conclusion: Taken together, this review provides a broad-based update of the available literature covering methamphetamine research over the past two decades and concludes with recommendations for future research., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

We hypothesized that treatment of pregnant rat dams with a dual reactive monoclonal antibody (mAb4G9) against (+)-methamphetamine [METH; equilibrium dissociation rate constant (KD) = 16 nM] and (+)-amphetamine (AMP; KD = 102 nM) could confer maternal and fetal protection from brain accumulation of both drugs of abuse. To test this hypothesis, pregnant Sprague-Dawley rats (on gestational day 21) received a 1 mg/kg i.v. METH dose, followed 30 minutes later by vehicle or mAb4G9 treatment. The mAb4G9 dose was 0.56 mole-equivalent in binding sites to the METH body burden. Pharmacokinetic analysis showed baseline METH and AMP elimination half-lives were congruent in dams and fetuses, but the METH volume of distribution in dams was nearly double the fetal values. The METH and AMP area under the serum concentration-versus-time curves from 40 minutes to 5 hours after mAb4G9 treatment increased >7000% and 2000%, respectively, in dams. Fetal METH serum did not change, but AMP decreased 23%. The increased METH and AMP concentrations in maternal serum resulted from significant increases in mAb4G9 binding. Protein binding changed from ∼15% to > 90% for METH and AMP. Fetal serum protein binding appeared to gradually increase, but the absolute fraction bound was trivial compared with the dams. mAb4G9 treatment significantly reduced METH and AMP brain values by 66% and 45% in dams and 44% and 46% in fetuses (P < 0.05), respectively. These results show anti-METH/AMP mAb4G9 therapy in dams can offer maternal and fetal brain protection from the potentially harmful effects of METH and AMP., (Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics.)

Background: Methamphetamine (METH) abuse is a growing health problem worldwide, and METH use during pregnancy not only endangers the mother's health but also the developing fetus. To provide better insight into these risks, we performed the following experiments., Method: First, we investigated how sex influences the pharmacokinetics of METH and amphetamine (AMP) in male and female rats. Subsequently, we simulated chronic exposure of prenatal infants to METH abuse by investigating brain and plasma levels of METH and AMP in dams and pups. Finally, we modeled chronic exposure of infants to METH via breast milk and investigated sex differences in pups with regard to drug levels and possible sensitization effect of chronic prenatal METH co-treatment., Results: We observed significantly higher levels of METH and AMP in the plasma and brain of female rats compared to males. Additionally, brain concentrations of METH and AMP in pups exposed to METH prenatally were equivalent to 62.13% and 37.78% relative to dam, respectively. Plasma concentrations of AMP where equivalent to 100% of the concentration in dams, while METH was equivalent to only 36.98%. Finally, we did not observe a significant effect relative to sex with regard to METH/AMP levels or sensitization effects linked to prenatal METH exposure., Conclusion: We demonstrated that female rats display higher levels of METH and AMP, thus indicating a greater risk of addiction and toxicity. Furthermore, our data show that pups are exposed to both METH and AMP following dam exposure., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

This in vitro investigation evaluated [(14)C] - d-methamphetamine hydrochloride ([(14)C]-meth HCl) transfer from contaminated vinyl tile (non-porous and smooth) and upholstery fabric (rough and loose) to human skin. (14)C-Meth HCl transfer rate from vinyl to skin was rapid; a contact duration as brief as 15s resulted in measurable radioactivity in the skin and receptor fluid samples. In contrast, the transfer from fabric occurred more slowly: the amount of [(14)C]-meth HCl that was transferred from dry fabric after 2-h skin contact was one-fifth the amount transferred from vinyl after 5-min contact time. With moistened fabric, the transfer efficiency to skin after 2-h contact was seven times greater than that of dry fabric. While the duration of surface-skin contact appeared to affect the total dermal absorption of [(14)C]-meth HCl, it had little effect on the time point of maximum transdermal absorption. [(14)C]-meth HCl retained in skin continued to be absorbed after the contaminated material was removed. Mass balance in these studies was approximately 96%. In conclusion, [(14)C]-meth HCl penetrates into/through human skin quickly following skin contact with contaminated materials. The porosity of the contact surface and the moisture content appears to alter the degree of transfer and dermal penetration., (Copyright © 2014. Published by Elsevier Ltd.)

3,4-Methylenedioxymethamphetamine (MDMA) is a widely abused illicit drug that can cause severe and even fatal adverse effects. However, interest remains for its possible clinical applications in posttraumatic stress disorder and anxiety treatment. Preclinical studies to determine MDMA's safety are needed. We evaluated MDMA's pharmacokinetics and metabolism in male rats receiving 2.5, 5, and 10 mg/kg s.c. MDMA, and the associated pharmacodynamic consequences. Blood was collected via jugular catheter at 0, 0.5, 1, 2, 4, 6, 8, 16, and 24 hours, with simultaneous serotonin (5-HT) behavioral syndrome and core temperature monitoring. Plasma specimens were analyzed for MDMA and the metabolites (±)-3,4-dihydroxymethamphetamine (HHMA), (±)-4-hydroxy-3-methoxymethamphetamine (HMMA), and (±)-3,4-methylenedioxyamphetamine (MDA) by liquid chromatography-tandem mass spectrometry. After 2.5 mg/kg MDMA, mean MDMA Cmax was 164 ± 47.1 ng/ml, HHMA and HMMA were major metabolites, and <20% of MDMA was metabolized to MDA. After 5- and 10-mg/kg doses, MDMA areas under the curve (AUCs) were 3- and 10-fold greater than those after 2.5 mg/kg; HHMA and HMMA AUC values were relatively constant across doses; and MDA AUC values were greater than dose-proportional. Our data provide decisive in vivo evidence that MDMA and MDA display nonlinear accumulation via metabolic autoinhibition in the rat. Importantly, 5-HT syndrome severity correlated with MDMA concentrations (r = 0.8083; P < 0.0001) and core temperature correlated with MDA concentrations (r = 0.7595; P < 0.0001), suggesting that MDMA's behavioral and hyperthermic effects may involve distinct mechanisms. Given key similarities between MDMA pharmacokinetics in rats and humans, data from rats can be useful when provided at clinically relevant doses.

Case Report: A 20-year-old woman presented with the chest pain, nausea, respiratory strange feeling, and a large quantity of sweating. On the stimulant zone of 8 groups of drugs of Triage DOA screening it showed an equivocal positivity while all of the other zones gave negative results. She denied taking drugs. No injection scar was found. And she was then hospitalized because little was known about her symptoms. When the unconscious patient was discovered at rest room inside hospital the next day, she was transferred to emergency and critical care center. In the same screening test positivity on the stimulant zone was observed, and furthermore both amphetamine and methamphetamine were detected by GCMS analysis. For 4 days positivity on the stimulant zone lasted. From the fact of disturbance of consciousness, restlessness, excitation and tachycardia, respiration disorder, and the pupil dilatation drug poisoning was deeply suspected., Discussion: While the stimulant zone of Triage DOA showed the equivocal positivity when 7 hours has elapsed until she became aware of abnormality and hospitalized, in the same screening of 30 hours later positivity was verified clearly. Several problems derived from the detection method, pharmacokinetic factors and pharmacodynamic aspect were discussed as for the difference of the results detected.

Objective: Since cocaine and psychostimulant dependence are related to increased dopamine release, antipsychotics have been tried to reduce their reinforcing properties. A meta-analysis was undertaken to assess the efficacy and tolerability of antipsychotics in cocaine- or stimulant-dependent patients., Data Sources: We searched PubMed, Cochrane Library databases, and PsycINFO from database inception until June 24, 2013, using the following keywords: (randomized OR random OR randomly) AND (placebo) AND (methylphenidate OR cocaine OR methamphetamine OR amphetamine OR 3,4-methylenedioxymethamphetamine) AND (dependence OR abuse) AND (antipsychotic OR neuroleptic OR 34 specific antipsychotic names)., Study Selection: Included were randomized, placebo-controlled trials of antipsychotics lasting at least 2 weeks in patients with primary cocaine or psychostimulant dependence. Of 363 hits, we removed 316 duplicates, 20 references based on abstract/title, and 13 ineligible full-text articles, retaining 14 trials for this meta-analysis., Data Extraction: Two authors independently extracted the data. Coprimary outcomes included degree of substance use and lack of abstinence. Risk ratio (RR), 95% CI, and standardized mean difference were calculated., Results: Ten studies in patients with primary cocaine dependence (risperidone = 5, olanzapine = 3, reserpine = 2; n = 562) and 4 in those with amphetamine/methamphetamine dependence (aripiprazole = 4; n = 179) were meta-analyzed (14 studies, total n = 741). When study results were pooled together, antipsychotics did not differ from placebo in regard to cocaine use days and lack of cocaine or amphetamine/methamphetamine abstinence, severity of addiction, cocaine or amphetamine/methamphetamine craving, Clinical Global Impressions-Severity of Illness (CGI-S) scores, depression, anxiety, compliance, all-cause discontinuation, and several side effects. However, antipsychotics caused more intolerability-related discontinuation than placebo (P = .0009). Individually, aripiprazole was superior to placebo in regard to CGI-S (P = .001), while olanzapine was inferior to placebo in regard to cocaine craving (P = .03) and risperidone was inferior to placebo in regard to depression (P = .002)., Conclusions: Antipsychotics had no advantages over placebo in regard to cocaine use and cocaine or psychostimulant abstinence or craving, while causing more intolerability-related discontinuations., (© Copyright 2013 Physicians Postgraduate Press, Inc.)

Behavioral sensitization has been widely studied in animal models and is theorized to reflect neural modifications associated with human psychostimulant addiction. While the mesolimbic dopaminergic pathway is known to play a role, the neurochemical mechanisms underlying behavioral sensitization remain incompletely understood. In this study, we conducted the first metabolomics analysis to globally characterize neurochemical differences associated with behavioral sensitization. Methamphetamine (MA)-induced sensitization measures were generated by statistically modeling longitudinal activity data for eight inbred strains of mice. Subsequent to behavioral testing, nontargeted liquid and gas chromatography-mass spectrometry profiling was performed on 48 brain samples, yielding 301 metabolite levels per sample after quality control. Association testing between metabolite levels and three primary dimensions of behavioral sensitization (total distance, stereotypy and margin time) showed four robust, significant associations at a stringent metabolome-wide significance threshold (false discovery rate, FDR <0.05). Results implicated homocarnosine, a dipeptide of GABA and histidine, in total distance sensitization, GABA metabolite 4-guanidinobutanoate and pantothenate in stereotypy sensitization, and myo-inositol in margin time sensitization. Secondary analyses indicated that these associations were independent of concurrent MA levels and, with the exception of the myo-inositol association, suggest a mechanism whereby strain-based genetic variation produces specific baseline neurochemical differences that substantially influence the magnitude of MA-induced sensitization. These findings demonstrate the utility of mouse metabolomics for identifying novel biomarkers, and developing more comprehensive neurochemical models, of psychostimulant sensitization., (© 2013 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.)

Recreational use of the drug 4-methylmethcathinone (mephedrone; 4-MMC) became increasingly popular in the United Kingdom in recent years, spurred in part by the fact that it was not criminalized until April 2010. Although several fatalities have been associated with consumption of 4-MMC and cautions for recreational users about its addictive potential have appeared on Internet forums, very little information about abuse liability for this drug is available. This study was conducted to determine if 4-MMC serves as a reinforcer in a traditional intravenous self-administration model. Groups of male Wistar and Sprague-Dawley rats were prepared with intravenous catheters and trained to self-administer 4-MMC in 1-hour sessions. Per-infusion doses of 0.5 and 1.0 mg/kg were consistently self-administered, resulting in greater than 80% discrimination for the drug-paired lever and mean intakes of about 2-3 mg/kg/hour. Dose-substitution studies after acquisition demonstrated that the number of responses and/or the total amount of drug self-administered varied as a function of dose. In addition, radiotelemetry devices were used to show that self-administered 4-MMC was capable of increasing locomotor activity (Wistar) and decreasing body temperature (Sprague-Dawley). Pharmacokinetic studies found that the T1/2 of 4-MMC was about 1 hour in vivo in rat plasma and 90 minutes using in vitro liver microsomal assays. This study provides evidence of stimulant-typical abuse liability for 4-MMC in the traditional pre-clinical self-administration model., (© 2013 The Authors, Addiction Biology © 2013 Society for the Study of Addiction.)

Introduction: Methylone (3,4-methylenedioxymethcathinone) is a new psychoactive substance and an active ingredient of "legal highs" or "bath salts". We studied the pharmacokinetics and locomotor activity of methylone in rats at doses equivalent to those used in humans., Material and Methods: Methylone was administered to male Sprague-Dawley rats intravenously (10mg/kg) and orally (15 and 30 mg/kg). Plasma concentrations and metabolites were characterized by LC/MS and LC-MS/MS fragmentation patterns. Locomotor activity was monitored for 180-240 min., Results: Oral administration of methylone induced a dose-dependent increase in locomotor activity in rats. The plasma concentrations after i.v. administration were described by a two-compartment model with distribution and terminal elimination phases of α=1.95 h(-1) and β=0.72 h(-1). For oral administration, peak methylone concentrations were achieved between 0.5 and 1h and fitted to a flip-flop model. Absolute bioavailability was about 80% and the percentage of methylone protein binding was of 30%. A relationship between methylone brain levels and free plasma concentration yielded a ratio of 1.42 ± 0.06, indicating access to the central nervous system. We have identified four Phase I metabolites after oral administration. The major metabolic routes are N-demethylation, aliphatic hydroxylation and O-methylation of a demethylenate intermediate., Discussion: Pharmacokinetic and pharmacodynamic analysis of methylone showed a correlation between plasma concentrations and enhancement of the locomotor activity. A contribution of metabolites in the activity of methylone after oral administration is suggested. Present results will be helpful to understand the time course of the effects of this drug of abuse in humans., (Copyright © 2013 Elsevier Inc. All rights reserved.)