Development and validation of a high-performance thin-layer chromatography method for detection of sibutramine in dietary supplements.

INTRODUCTION: In the period between 1997 and 2010, sibutramine-containing drugs were widely prescribed for obesity and over-weight management. Due to safety concerns, in 2010 all medicines containing sibutramine were urgently withdrawn from the USA and European pharmaceutical market. Although sibutramine is no longer available in pharmaceutical products, there have been numerous reports of mislabeled weight-loss dietary supplements containing sibutramine.

Detection of amfepramone and its metabolite cathinone in human hair: Application to a uthentic cases of amfepramone use.

In recent years, overseas anti-obesity drugs including amfepramone have flowed into China through the internet or personal import by travelers. Amfepramone is controlled in China and is not available as a pharmaceutical product. It is obtainable either through the internet or imported by individuals across the border. The abuse of amfepramone is causing serious health problems. A method for the detection and quantification of amfepramone and its metabolite cathinone in human hair was developed and fully validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Approximately 10 mg of hair was weighed and pulverized with extraction solvent (a mixture of methanol: acetonitrile: 2 mM ammonium formate [pH 5.3] [25:29:46, v/v/v]). The limit of detection (LOD) and the limit of quantitation (LOQ) were 5 and 10 pg/mg, respectively. The method was linear over a concentration range from 10 to 10,000 pg/mg. The accuracy varied from -9.3% to 2.3%, with acceptable intra- and inter-day precision. The validated method was successfully applied to 17 authentic cases. The amfepramone concentrations ranged from 11.7 to 209 pg/mg, with a median of 30.2 pg/mg, and the hair cathinone concentrations ranged from 11.9 to 507 pg/mg, with a median of 54.0 pg/mg. This is the first report of amfepramone concentrations in human hair from amfepramone users. Cathinone can be incorporated into hair after amfepramone use.

Visual upconversion nanoparticle-based immunochromatographic assay for the semi-quantitative detection of sibutramine.

Immunochromatographic assay (ICA) has been used widely for the onsite monitoring of illegal additives due to its simplicity, speed, and low cost. However, a scanner is commonly required for ICA to achieve quantitative results. In this work, we developed a visual semi-quantitative ICA for sibutramine, a banned additive in diet foods, without the need for a scanner for measurement. Monoclonal antibodies specific for sibutramine were raised and conjugated with upconversion nanoparticles (UCNPs) as the luminescent tracer. ICA was developed by employing multiple test lines to achieve the semi-quantitative detection of sibutramine. Based on the optimal conditions, the cutoff levels (limit of quantitation, LOQ) of T1 line, T2 line, T3 line, and T4 line were 0.02 µg/mL, 0.15 µg/mL, 1.0 µg/mL, and 7.5 µg/mL, respectively, in buffer system. The ICA demonstrated a LOQ at 0.2 mg/kg for sibutramine in diet food samples. The assay (including pretreatment) can be finished within 30 min without the aid of other instruments, except a laser pen. No false positive or false negative results were observed. The results indicated that the proposed method was reliable, simple, and rapid for the screening of sibutramine abuse in diet food samples.

Microwave-assisted extraction and differential scanning calorimetry in the chemical identification of sliming agents apprehended in the south region of Brazil.

Over the past decades, consume of slimming agents considerably increased in several countries, including Brazil, due to weight-loss and stimulant properties. Since these drugs are controlled to prevent illicit and indiscriminate use, there is a parallel illegal market that uses the Internet and irregular pharmacies in order to distribute these formulations. Slimming agents produced by these illegal sources are known for being manufactured with little or none quality control resulting in uncertain and unknown formulations. For forensic purposes, apprehended pharmaceuticals have to undergo a process of chemical identification that can be difficult due to its complex matrix. In this sense, application of assisted energies in the extraction step such as microwave irradiation can be a promising method to increase the recuperation of the target molecules of the sample. Therefore, the aim of this research was to identify four slimming agents apprehended in Brazil by means of visual inspection, Fourier Transform Infrared Spectroscopy, Differential Scanning Calorimetry and Gas Chromatography - Mass Spectrometry. Moreover, the efficiency of solid-liquid extraction and microwave-assisted extraction was compared. It should be noted that our work was one of the few to use Differential Scanning Calorimetry and the application of microwave irradiation in the analysis of apprehended materials. Results showed that the majority of the samples was counterfeit being composed of one or several adulterants or contaminants. Initially, visual inspection resourcefully screened the slimming agents for possible signs of falsification, however it failed to detect fraudulent products that were very similar to veridical medicines. Sequentially, Fourier Transform Infrared Spectroscopy detected functional groups present in the samples while the presence or absence of the alleged active ingredients were successfully measured with Differential Scanning Calorimetry and, thus, providing a full chemical screening of the apprehended materials. Gas Chromatography- Mass Spectrometry confirmed the presence of adulterants such as caffeine, fluoxetine and phenolphthalein as well as contaminants such as sulfurol in the falsified samples. Finally, comparison of extraction procedures indicated that microwave-assisted extraction increased the recovery of compounds detected in chromatographic analysis to a greater extent than solid-liquid extraction.

Over-the-Counter Herbal Weight Loss Supplements in Egypt: Label Claim, Microbiological and Pharmaceutical Quality, and Safety Assessments.

OBJECTIVES: Nutraceuticals are advertised and sold with the label claim of being natural and safe herbal products. Due to the absence of clear regulations and guidelines for safety assessments of these products, nutraceuticals are commonly adulterated in order to increase sales. The objective of the current study was to design a comprehensive evaluation system to assess the safety, efficacy, authenticity according to label claim, and pharmaceutical quality of herbal slimming products in between 2015 and 2017. METHODS: We designed a comprehensive assessment system to evaluate the safety, authenticity according to label claim, and pharmaceutical quality of slimming nutraceuticals. Six different popular products were evaluated (Zotreem Plus®, Zotreem Extra®, Malaysian Super Slim®, AB Slim®, Chinese Super Slim®, and Metabolites®). The pharmaceutical evaluation included analyzing the samples via high-performance liquid chromatography to determine any possible adulterants. Additionally, the products' physical properties were assessed via pharmacopeial tests. Finally, a microbial evaluation and a cross-sectional observational retrospective prevalence study were conducted to assess the products' safety and efficacy. -Results: The tested products were found to be adulterated with unreported active pharmaceutical ingredients such as sibutramine, sildenafil, phenolphthalein, and orlistat. Furthermore, they contained heterogeneous amounts of adulterants and exhibited an unsatisfactory pharmaceutical and microbial quality. Finally, the observational survey conducted on users showed that high percentages of participants suffered from common side effects such as depression, diarrhea, and hypertension. CONCLUSIONS: These products threaten the health of consumers. There is a need to raise awareness of the lethal consequences of illegal nutraceuticals.

Validation of a rapid and simple high-performance liquid chromatography-electrospray ionization-mass spectrometry method for simultaneous analysis of 15 key chemicals in slimming foods and herbal products.

A rapid and simple high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed for simultaneous analysis of 15 key chemicals in slimming foods and herbal products. These chemicals were strictly restricted adulterants (phenolphthalein, sibutramine, fenfluramine, clopamide, ephedrine, norpseudoephedrine, caffeine and phenformin) and physiologically relevant active components (l-carnitine, nuciferine, aloe-emodin, rhein, emodin, chrysophanol and physcion). In multi-day validations, intra- (n = 5) and inter-day precision (n = 3), limits of detection and limits of quantification for all analytes were 0.60-7.22%, 0.75-9.45%, 0.09-10 µg/L and 0.30-33.3 µg/L, respectively. Mean recovery ranged from 71.4% to 116% for all analytes in three representative samples. The method was validated on 17 samples including 12 kinds of slimming foods and five kinds of herbal products, and was shown to be ideal for routine quantification of 15 key chemicals in slimming foods and herbal products, providing an efficient strategy for quality control and food safety evaluation of weight reducing supplements.

Application of HRAM screening and LC-MS/MS confirmation of active pharmaceutical ingredient in "natural" herbal supplements.

The growing market of herbal remedies worldwide could pose severe problems to consumers' health due to the possible presence of potentially harmful, undeclared synthetic substances or analogues of prescription drugs. The present work shows a simple but effective approach to unequivocally identify synthetic anorectic compounds in allegedly 'natural' herbal extracts, by exploiting liquid chromatography/time of flight (Q-TOF LC/MS) technology coupled to liquid chromatography/triple quadrupole (LC-MS/MS) confirmation and quantitation. The procedure was applied to five tea herbal extracts and pills sold as coadjutant for weigh loss. The method exploited liquid-liquid sample extraction (LLE) and separation in a C18 (2.1mm×150mm, 1.8µm) column. QTOF acquisitions were carried out both in scan mode and all ion MS/MS mode and results were obtained after search against ad hoc prepared library. Sibutramine, 4-hydroxyamphetamine, caffeine and theophylline were preliminary identified samples. Confirmation and quantitation of the preliminary identified compounds were obtained in LC-MS/MS after preparation of appropriated standards. Sibutramine, caffeine and theophylline were finally confirmed and quantitate.

A graphene tip coupled with liquid chromatography tandem mass spectrometry for the determination of four synthetic adulterants in slimming supplements.

Slimming supplements were popularly sold online driven by the increasement of obesity and the development of social networking platform. However, events of drug abuse in slimming supplements were also frequently reported. In this study, a graphene tip solid-phase extraction (Gtip SPE) and ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was established for determining fenfluramine, phenolphthalein, bumetanide, and sibutramine in slimming supplements. It was validated in terms of linearity (0.9985-0.9995), LOD (1.8ngmL-1), LOQ (5.6ngmL-1), intra-day precision (<5.1%), inter-day precision (<7.3%), and recovery (82.9-95.2%). Sibutramine is the most commonly used drug, which was detected in Bihais, Galong, and Aolist, with content 12.4, 3.6, 20.3mgg-1, respectively. Phenolphthalein was also found with content lower than 5.2mgg-1. The successful application of Gtip SPE and UPLC-MS/MS method indicated its advantage in analyzing low level of contaminates resulted from violation of regulation.

Epicatechin, procyanidins, cocoa, and appetite: a randomized controlled trial.

BACKGROUND: In 2 randomized controlled trials, it was reported that dark chocolate acutely decreased appetite in human subjects, but the authors did not assess the types or concentrations of cocoa compounds that are needed. Other studies have suggested that the cocoa compounds epicatechin and procyanidins may be involved. OBJECTIVE: We sought to test the hypotheses that, compared with placebo (an alkalized cocoa mixture containing essentially no epicatechin or procyanidins), the following beverages cause a decrease in appetite: 1) a nonalkalized cocoa mixture; 2) epicatechin plus placebo; and 3) procyanidins plus placebo. We measured the concentrations of cocoa compounds in all beverages. DESIGN: We used a 4-way randomized, crossover, placebo-controlled trial that was balanced for period and carryover effects in 28 healthy, young-adult men. We also conducted a smaller (n = 14), parallel, secondary randomized trial in which we explored the effects of higher doses of epicatechin and procyanidins. Our primary measure of appetite was ad libitum pizza intake 150 min after beverage ingestion. We used a linear mixed-model analysis. RESULTS: Intakes of beverages with the nonalkalized cocoa mixture that contained 0.6 mg epicatechin, 0.2 mg catechin, and 2.9 mg monomer-decamer procyanidins/kg body weight did not decrease pizza intake significantly (P = 0.29) compared with intake of the placebo. In the smaller secondary trial, a combination of epicatechin and the nonalkalized cocoa mixture that contained 1.6 mg epicatechin/kg body weight significantly decreased pizza intake by 18.7% (P = 0.04). CONCLUSIONS: Our nonalkalized cocoa mixture was associated with an acute decrease in food intake only after being supplemented with epicatechin. It is possible that epicatechin at a dose of >1.6 mg/kg body weight, alone or in concert with appropriate catalytic cocoa compounds, may be useful for helping people control their food intakes. This trial was registered at clinicaltrials.gov as NCT02408289.

A validated LC/UV method for the determination of four adulterating drugs in herbal slimming capsules.

A simple LC/UV method for the simultaneous identification and quantification of Fluoxetine, Tiratricol, Benfluorex and Pseudoephedrine in slimming formulation is proposed. The method demonstrated effective in the analyses of herbal mixtures marketed in Italy as slimming capsules. Sixteen different herbal mixtures, selected among the most frequently compounded in Italian pharmacies, were tested as matrices. HPLC analyses were performed in a gradient mode on a C18 stationary phase The method was validated for accuracy, precision, linearity and selectivity. The limits of detection (LOD) were 3.4 µg/mL for Pseudoephedrine, 1.1 µg/mL for Triac, 0.9 µg/mL for Fluoxetine, and 0.8 µg/mL for Benfluorex. Repeatability and intermediate precision, expressed as percent of relative standard deviation, ranged from 3 to 7 and from 7 to 12, respectively. Given these limits, the developed method is proposed for the simple and cost effective screening of herbal products illegally adulterated with these four drugs known to enhance slimming effects.

Comparison of three development approaches for Stationary Phase Optimised Selectivity Liquid Chromatography based screening methods Part I: A heterogeneous group of molecules (slimming agents in food supplements).

Three approaches for the development of a screening method to detect adulterated dietary supplement, based on Stationary Phase Optimised Selectivity Liquid Chromatography were compared for their easiness/speed of development and the performance of the optimal method obtained. This comparison was performed for a heterogeneous group of molecules, i.e. slimming agents (Part I) and a group of structural analogues, i.e. PDE-5 inhibitors (Part II). The first approach makes use of primary runs at one isocratic level, the second of primary runs in gradient mode and the third of primary runs at three isocratic levels to calculate the optimal combination of segments of stationary phases. In each approach the selection of the stationary phase was followed by a gradient optimisation. For the slimming agents, the heterogeneous group of molecules, the method obtained with the first approach was selected as optimal, based on the speed of development and the performance of the method. The method shows a good separation of the compounds, allowing the screening to be performed with diode array detection, and is fully compatible with mass spectrometry. The method was validated for its selectivity following the guidelines as described for the screening of pesticide residues and residues of veterinary medicines in food.

Near Infrared Spectroscopy Detection and Quantification of Herbal Medicines Adulterated with Sibutramine.

There is an increasing demand for herbal medicines in weight loss treatment. Some synthetic chemicals, such as sibutramine (SB), have been detected as adulterants in herbal formulations. In this study, two strategies using near infrared (NIR) spectroscopy have been developed to evaluate potential adulteration of herbal medicines with SB: a qualitative screening approach and a quantitative methodology based on multivariate calibration. Samples were composed by products commercialized as herbal medicines, as well as by laboratory adulterated samples. Spectra were obtained in the range of 14,000-4000 per cm. Using PLS-DA, a correct classification of 100% was achieved for the external validation set. In the quantitative approach, the root mean squares error of prediction (RMSEP), for both PLS and MLR models, was 0.2% w/w. The results prove the potential of NIR spectroscopy and multivariate calibration in quantifying sibutramine in adulterated herbal medicines samples.

Liquid chromatography-high resolution mass spectrometry (LC-HRMS) determination of stimulants, anorectic drugs and phosphodiesterase 5 inhibitors (PDE5I) in food supplements.

The paper describes a liquid chromatography/high resolution mass spectrometry LC/HRMS method for the simultaneous identification and quantification of stimulants (ephedrines, caffeine, anorectic drugs such as phentermine, phendimetrazine, phenmetrazine, fenfluramine, benfluorex, mephentermine, fencanfamine, sibutramine) and PDE5I (sildenafil, vardenafil and tadalafil) in food supplements using a benchtop Orbitrap mass spectrometer. The mass detector, with a nominal resolving power of 100,000 (FWHM at m/z 200), operated in full scan mode in ESI positive ionization mode. Analytes were identified by retention times, accurate masses and correspondence of experimental and calculated isotopic patterns. The limits of detection (LOD) obtained varied from 1 to 25 ng g(-1) and limits of quantification (LOQ) were 50 ng g(-1) for all compounds. The method was linear for all the analytes in the ranges from 50 to 2000 ng g(-1), giving correlation coefficients>0.99. Accuracy (intended as %E) and repeatability (% CV) were always lower than 15%. The method was applied to the analysis of 36 dietary supplements, revealing the presence of ephedrine and/or pseudoephedrine in four of them, caffeine in eight of them and sildenafil in four of them. In one case, ephedrine was not reported on the label of the dietary supplement, as well as for caffeine in other two cases. A further confirmation of the analytes identity in positive samples was obtained through in-source fragmentation and comparison of the obtained fragments and their relative abundances with those from certified standards. As the acquisition mode is full scan, it would be also possible to re-process a previously acquired datafile for the investigation of untargeted analytes.

Detection of sibutramine in adulterated dietary supplements using attenuated total reflectance-infrared spectroscopy.

Sibutramine is one of the most occurring adulterants encountered in dietary supplements with slimming as indication. These adulterated dietary supplements often contain a herbal matrix. When customs intercept these kind of supplements it is almost impossible to discriminate between the legal products and the adulterated ones, due to misleading packaging. Therefore in most cases these products are confiscated and send to laboratories for analysis. This results inherently in the confiscation of legal, non-adulterated products. Therefore there is a need for easy to use equipment and techniques to perform an initial screening of samples. Attenuated total reflectance-infrared (ATR-IR) spectroscopy was evaluated for the detection of sibutramine in adulterated dietary supplements. Data interpretation was performed using different basic chemometric techniques. It was found that the use of ATR-IR combined with the k-Nearest Neighbours (k-NN) was able to detect all adulterated dietary supplements in an external test set and this with a minimum of false positive results. This means that a small amount of legal products will still be confiscated and analyzed in a laboratory to be found negative, but no adulterated samples will pass the initial ATR-IR screening.

GC-MS and LC-(high-resolution)-MS(n) studies on the metabolic fate and detectability of camfetamine in rat urine.

Camfetamine (N-methyl-3-phenyl-norbornan-2-amine; CFA) belongs as amphetamine-type stimulant to the so-called new psychoactive substances. CFA is an analogue of fencamfamine, an appetite suppressant developed in the 1960s. The described effects of CFA are slight stimulation and increased vigilance and the side effects are tachycardia, paranoia, and sleeplessness. The aims of the presented work were to study the metabolic fate and the detectability of CFA in urine and to elucidate which cytochrome-P450 (CYP) isoenzymes are involved in the main metabolic steps. For metabolism studies, rat urine samples were isolated by solid-phase extraction without and after enzymatic cleavage of conjugates. The phase I metabolites were separated and identified after/without acetylation by gas chromatography-mass spectrometry (GC-MS) and/or liquid chromatography-high resolution-linear ion trap mass spectrometry (LC-HR-MS(n)), respectively, and the phase II metabolites by LC-HR-MS(n). From the identified metabolites, the following main metabolic pathways were deduced: N-demethylation, aromatic mono or bis-hydroxylation followed by methylation of one hydroxy group, hydroxylation of the norbornane ring, combination of these steps, and glucuronidation and/or sulfation of the hydroxy metabolites. The N-demethylation was catalyzed by CYP2B6, CYP2C19, CYP2D6, and CYP3A4, the aromatic hydroxylation by CYP2C19 and CYP2D6, and the aliphatic hydroxylation was catalyzed by CYP1A2, CYP2B6, CYP2C19, and CYP3A4. Finally, the intake of a common user's dose of CFA could be confirmed in rat urine using the authors' GC-MS and the LC-MS(n) standard urine screening approaches via CFA and several metabolites, with the hydroxy-aryl CFA and the corresponding glucuronide being the most abundant.

Aminorex associated with possible idiopathic pulmonary hypertension in a cocaine user.

The conversion of levamisole to aminorex in horses was first described in 2009 and, for the first time, confirmed in humans two years later by our laboratory. Aminorex and levamisole interfere with serotonin metabolism and both are proven cause of potentially fatal idiopathic pulmonary hypertension (IPH). Because most of the world's seizures of illicit cocaine is now contaminated with levamisole, this raises the possibility that users of levamisole adulterated cocaine users may be at risk for IPH. Here we describe the first case of IPH in a user of levamisole-contaminated cocaine. Levamisole and aminorex were both identified and quantified in hair and other biological specimens by means gas chromatography/mass spectrometry system (levamisole: urine, 75.05ng/mL; blood, 15.05ng/mL; brain, >0.15ng/g; liver, >0.15ng/g; hair, 12.15ngmg; aminorex: urine, 38.62ng/mL; blood, 8.92ng/mL, brain >0.15ng/g; liver, 0.15ng/g; hair 7.35ng/mg; cocaine, benzoylecgonine, morphine, 6-acetylmorphine, methadone, 2-ethylidine-1, 5-dimetil-3, 3 diphenylpyrrolidine were also detected). Moreover histological changes associated with IPH were observed in the lung. As IPH produces relatively non-specific symptoms in its early stages, this index case may serve as a harbinger of many more cases to come. It should also alert clinicians to the possibility that their patient may be suffering from this relatively rare disorder.

Simultaneous quantification of the glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK) receptor agonists in rodent plasma by on-line solid phase extraction and LC-MS/MS.

Peptide agonists of the glucagon-like peptide-1 receptor (GLP-1R) and the cholecystokinin-1 receptor (CCK1-R) have therapeutic potential because of their marked anorexigenic and weight lowering effects. Furthermore, recent studies in rodents have shown that co-administration of these agents may prove more effective than treatment either of the peptide classes alone. To correlate the pharmacodynamic effects to the pharmacokinetics of these peptide drugs in vivo, a sensitive and robust bioanalytical method is essential. Furthermore, the simultaneous determination of both analytes in plasma samples by a single method offers obvious advantages. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is well suited to this goal through its ability to simultaneously monitor multiple analytes through selected reaction monitoring (SRM). However, it is a challenge to find appropriate conditions that allow two peptides with widely disparate physiochemical properties to be simultaneously analyzed while maintaining the necessary sensitivity for their accurate plasma concentrations. Herein, we report an on-line solid phase extraction (SPE) LC-MS/MS method for simultaneous quantification of the CCK1-R agonist AC170222 and the GLP-1R agonist AC3174 in rodent plasma. The assay has a linear range from 0.0975 to 100ng/mL, with lower limits of quantification of 0.0975ng/mL and 0.195ng/mL for AC3174 and AC170222, respectively. The intra- and inter-day precisions were below 15%. The developed LC-MS/MS method was used to simultaneously quantify AC3174 and AC170222, the results showed that the terminal plasma concentrations of AC3174 or AC170222 were comparable between groups of animals that were administered with the peptides alone (247±15pg/mL of AC3174 and 1306±48pg/mL of AC170222), or in combination (222±32pg/mL and 1136±47pg/mL of AC3174 and AC170222, respectively). These data provide information on the drug exposure to aid in assessing the combination effects of AC3174 and AC170222 on rodent metabolism.

Monitoring of 29 weight loss compounds in foods and dietary supplements by LC-MS/MS.

Because of the rapid growth in dietary supplement availability and public concern for weight control, the investigation of foods and various dietary supplements illegally adulterated with weight loss compounds has become increasingly important. A total of 29 weight loss compounds, including sennoside, sibutramine, ephedrine and their analogues, found to be adulterated in foods and dietary supplements were simultaneously examined by LC-MS/MS. The 188 samples were collected between 2009 and 2012 in South Korea, and method validation was performed to determine the adulterants to the weight loss compounds. LODs, LOQs and linearity ranged from 0.03 to 7.5 ng ml⁻¹, from 0.08 to 30.00 ng ml⁻¹, and from 0.990 to 0.999, respectively. The results showed that nine weight loss compounds, namely bisacodyl, desmethylsibutramine, didesmethylsibutramine, ephedrine, fluoxetine, pseudoephedrine, sennoside A, sennoside B and sibutramine, were detected in 62 of all collected samples and were found in order of frequency as follows: sibutramine, 25.7%; sennoside A, 22.9%; sennoside B, 20.0%; fluoxetine, 8.6%; desmethylsibutramine, 7.1%; bisacodyl, ephedrine, and pseudoephedrine, 4.3%; and didesmethylsibutramine, 2.9%. Sibutramine, which was the most frequently found adulterant, ranged in levels from 0.03 to 132.40 mg g⁻¹ (2010), from 0.88 to 76.2 mg g⁻¹ (2011), and from 0.07 to 0.24 mg g⁻¹ (2012). Although the concentrations of most compounds ranged widely, some compounds such as bisacodyl and fluoxetine were found at high concentrations in several samples.

Effect of mazindol on extracellular dopamine concentration in human brain measured by PET.

RATIONALE: Mazindol, an appetite suppressant, inhibits the reuptake of dopamine in the synaptic cleft. It has been considered that mazindol might enhance dopamine transmission in the human brain. However, there has been no study that investigated the extracellular dopamine concentration in vivo. OBJECTIVE: Using positron emission tomography (PET), we aimed to measure the effect of mazindol on the extracellular dopamine concentration and to evaluate how mazindol affects the dopamine system in the healthy human brain. METHODS: Eleven healthy individuals (six males, five females, age 30.9 ± 4.9 years) were enrolled in this study. Each participant was scanned with [(11)C]raclopride on 1 day without any medicine as baseline condition, and on another day with mazindol as drug condition. In the drug condition, participants took mazindol 0.5 mg (N = 5) or 1.5 mg (N = 6) 2 h before the PET scan. Plasma concentrations of mazindol were measured before the injection of [(11)C]raclopride, and urine concentrations of mazindol were measured after the scan. RESULTS: After taking mazindol, the calculated decrease in binding potential (ΔBP) in the striatum was 1.74 % for 0.5 mg and 8.14 for 1.5 mg, and the correlation with the blood concentration of mazindol was significant (P = 0.0016, R (2) = 0.69). ΔBP was not significantly correlated with the urine concentration of mazindol (P = 0.84, R (2) = 0.005). CONCLUSIONS: Mazindol increased the extracellular concentration of dopamine in the human brain, and its effect was dose dependent. A single administration of mazindol, even at usual dosage, elevated dopamine concentration similarly to other addictive drugs, suggesting that the risk of dependence may increase with the mazindol dose.