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Introduction: 123 I-FP-CIT ( 123 I-Ioflupane) SPECT shows strong accumulation in the striatum, but morphological standardization is challenging due to low accumulation outside the striatum, particularly in subjects with marked striatal decline. In this study, morphological standardization without MRI was achieved using the adaptive template registration (ATR) method to create a subject-specific optimized template with weighted images of normal-type and egg-shape-type templates. The accuracy of a quantitative method for calculating the ratio with nonspecific accumulation in the occipital lobe was evaluated by placing voxels-of-interest (VOI) on standardized images, particularly targeting the striatum., Methods: The average images of eight subjects, demonstrating normal-type and egg-shape-type tracer accumulation in 123 I-Ioflupane SPECT, were utilized as normal and disease templates, respectively. The study included 300 subjects that underwent both 123 I-Ioflupane SPECT and MRI for the diagnosis of suspected Parkinson's disease or for exclusion diagnosis. Morphological standardization of SPECT images using structural MRI (MRI-based method) was considered the standard of truth (SOT). Three morphological standardizations without MRI were conducted. The first involved conventional morphological standardization using a normal template (fixed template method), the second employed the ATR method, with a weighted template, and the third used the split-ATR method, processing the left and right striatum separately to address asymmetrical accumulation. VOIs were set on the striatum, caudate, putamen as regions of specific accumulation, and on the occipital lobe as a reference region for nonspecific accumulation., Results: Results showed significant and robust linearity in the striatal accumulation ratios for all templates when compared with the occipital lobe accumulation ratio when using the MRI-based method. Comparing intra-class correlations for different linearities, the ATR method and split-ATR method demonstrated higher linearity in the striatum, caudate, and putamen. The split-ATR method showed similar improvements, although more linearity than some of the ATR methods; the effectiveness of the Split-ATR method may vary by image quality, and further validation of its effectiveness in diverse asymmetric accumulation cases seemed warranted., Conclusion: The use of optimized templates, such as the ATR and split-ATR methods, improved reproducibility in fully automated processing and demonstrated superior linearity compared to that of MRI-based method, in the ratio to the occipital lobe. The ATR method, which enables morphological standardization when using SPECT images only, proved highly reproducible for clinical quantitative analysis of striatal accumulation, facilitating its clinical use., (© 2024. The Author(s).)

Ethnic differences exist among patients with Parkinson disease (PD). PD is more common in the White than the African American population. This study aimed to explore whether differences exist in [ 123 I]ioflupane binding, which reflects dopamine transporter binding, between African American and White individuals. Methods: Medical charts were reviewed for patients who underwent [ 123 I]ioflupane SPECT imaging as part of routine practice in a single academic medical center. All images were visually graded as showing normal or abnormal presynaptic dopaminergic function (normal or abnormal scan status). Quantitative [ 123 I]ioflupane uptake as measured by the specific binding ratios in the right and left striata and their subregions (caudate nucleus and anterior and posterior putamen) and by bilateral putamen-to-caudate ratios were compared between African American and White patients using multiple linear regression adjusted for age, sex, and abnormal scan status. Additional models included an ethnicity-by-abnormal-scan-status interaction term to determine whether abnormal scan status was modulated by ethnicity effect. Results: The percentage of patients with abnormal scan status was comparable between African American and White patients. Compared with White patients ( n = 173), African American patients ( n = 82) had statistically significantly higher uptake as measured by specific binding ratios in the right and left striata and some of their subregions (right and left caudate nuclei and right posterior putamen). Ethnicity-by-abnormal-scan-status interactions were not statistically supported for any models. Conclusion: We observed differences in [ 123 I]ioflupane binding between African American and White patients independent of presynaptic dopaminergic dysfunction status. Future studies are needed to examine whether and how ethnicity affects dopamine transporter binding activities and its clinical relevance., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)

Purpose: We hypothesized that severe tau burden in brain regions involved in direct or indirect pathways of the basal ganglia correlate with more severe striatal dopamine deficiency in four-repeat (4R) tauopathies. Therefore, we correlated [ 18 F]PI-2620 tau-positron-emission-tomography (PET) imaging with [ 123 I]-Ioflupane single-photon-emission-computed tomography (SPECT) for dopamine transporter (DaT) availability., Methods: Thirty-eight patients with clinically diagnosed 4R-tauopathies (21 male; 69.0 ± 8.5 years) and 15 patients with clinically diagnosed α-synucleinopathies (8 male; 66.1 ± 10.3 years) who underwent [ 18 F]PI-2620 tau-PET and DaT-SPECT imaging with a time gap of 3 ± 5 months were evaluated. Regional Tau-PET signals and DaT availability as well as their principal components were correlated in patients with 4R-tauopathies and α-synucleinopathies. Both biomarkers and the residuals of their association were correlated with clinical severity scores in 4R-tauopathies., Results: In patients with 4R-tauopathies, [ 18 F]PI-2620 binding in basal ganglia and midbrain regions was negatively associated with striatal DaT availability (i.e. globus pallidus internus and putamen (β =  - 0.464, p = 0.006, Durbin-Watson statistics = 1.824) in a multiple regression model. Contrarily, [ 18 F]PI-2620 binding in the dentate nucleus showed no significant regression factor with DaT availability in the striatum (β = 0.078, p = 0.662, Durbin-Watson statistics = 1.686). Patients with α-synucleinopathies did not indicate any regional associations between [ 18 F]PI-2620-binding and DaT availability. Higher DaT-SPECT binding relative to tau burden was associated with better clinical performance (β =  - 0.522, p = 0.011, Durbin-Watson statistics = 2.663) in patients with 4R-tauopathies., Conclusion: Tau burden in brain regions involved in dopaminergic pathways is associated with aggravated dopaminergic dysfunction in patients with clinically diagnosed primary tauopathies. The ability to sustain dopamine transmission despite tau accumulation may preserve motor function., (© 2024. The Author(s).)

This study aimed to explore the beneficial effects of the antioxidant N-acetylcysteine (NAC) on the degenerated dopamine system. The short- and long-term regulatory mechanisms of NAC on the 6-OHDA hemiparkinsonian rat model were longitudinally investigated by performing positron emission tomography (PET) imaging using the specific dopamine transporter (DAT) radioligand [ 18 F]FE-PE2I. The results demonstrate that after a unilateral dopamine insult NAC has a strong influence on the non-lesioned hemisphere by decreasing the levels of DAT in the striatum early after the lesion. We interpret this early and short-term decrease of DAT in the healthy striatum of NAC-treated animals as a beneficial compensatory effect induced by NAC., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Purpose: The dopamine transporter (DAT) is a marker of the occurrence and development of Parkinson's disease (PD) and other diseases with nigrostriatal degeneration. 2β-Carbomethoxy-3β-(4-chlorophenyl)-8-(2-[ 18 F]-fluoroethyl)nortropane ([ 18 F]FECNT), an 18 F-labelled tropane derivative, was reported to be a useful positron-emitting probe for DAT. However, the rapid formation of brain-penetrating radioactive metabolites is an impediment to the proper quantitation of DAT in PET studies with [ 18 F]FECNT. Deuterium-substituted analogues have presented better in vivo stability to reduce metabolites. This study aimed to synthesize a deuterium-substituted DAT radiotracer, [ 18 F]FECNT-d 4 , and to make a preliminary investigation of its properties as a DAT tracer in vivo., Procedures: The ligand [ 18 F]FECNT-d 4 was obtained by one-step radiolabelling reaction. The lipophilicity was measured by the shake-flask method. Binding properties of [ 18 F]FECNT-d 4 were estimated by in vitro binding assay, biodistribution, and microPET imaging in rats. In vivo stability of [ 18 F]FECNT-d 4 was estimated by radio-HPLC., Results: [ 18 F]FECNT-d 4 was synthesized at an average activity yield of 46 ± 17 % (n = 15) and the molar activity was 67 ± 12 GBq/μmol. The deuterated tracer showed suitable lipophilicity and the ability to penetrate the blood-brain barrier (brain uptake of 1.72 % ID at 5 min). [ 18 F]FECNT-d 4 displayed a high binding affinity for DAT comparable to that of [ 18 F]FECNT in rat striatum homogenates. Biodistribution results in normal rats showed that [ 18 F]FECNT-d 4 exhibited a higher ratio of the target to non-target (striatum/cerebellum) at 15 min post administration (5.00 ± 0.44 vs 3.84 ± 0.24 for [ 18 F]FECNT-d 4 vs [ 18 F]FECNT). MicroPET imaging studies of [ 18 F]FECNT-d 4 in normal rats showed that the ligand selectively localized to DAT-rich striatal regions and the accumulation could be blocked with DAT inhibitor. Furthermore, in the unilateral PD model rat, a significant reduction of the signal was found in the lesioned side relative to the unlesioned side. Striatal standardized uptake value of [ 18 F]FECNT-d 4 remained ~4.02 in the striatum between 5 and 20 min, whereas that of [ 18 F]FECNT fell rapidly from 4.11 to 2.95. Radio-HPLC analysis of the plasma demonstrated better in vivo stability of [ 18 F]FECNT-d 4 than [ 18 F]FECNT., Conclusion: The deuterated compound [ 18 F]FECNT-d 4 may serve as a promising PET imaging agent to assess DAT-related disorders., (© 2021. World Molecular Imaging Society.)

Food can alter drug absorption and impact safety and efficacy. Besides conducting clinical studies, in vitro approaches such as biorelevant solubility and dissolution testing and in vivo dog studies are typical approaches to estimate a drug's food effect. The use of physiologically based pharmacokinetic models has gained importance and is nowadays a standard tool for food effect predictions at preclinical and clinical stages in the pharmaceutical industry. This manuscript is part of a broader publication from the IQ Consortium's food effect physiologically based pharmacokinetic model (PBPK) modeling working group and complements previous publications by focusing on cases where the food effect was predicted with low confidence. Pazopanib-HCl, trospium-Cl, and ziprasidone-HCl served as model compounds to provide insights into why several food effect predictions failed in the first instance. Furthermore, the manuscript depicts approaches whereby PBPK-based food effect predictions may be improved. These improvements should focus on the PBPK model functionality, especially better reflecting fasted- and fed-state gastric solubility, gastric re-acidification, and complex mechanisms related to gastric emptying of drugs. For improvement of in vitro methodologies, the focus should be on the development of more predictive solubility, supersaturation, and precipitation assays. With regards to the general PBPK modeling methodology, modelers should account for the full solubility profile when modeling ionizable compounds, including common ion effects, and apply a straightforward strategy to account for drug precipitation.

Introduction: Increasing evidence suggests that neuroinflammation is active in Parkinson disease (PD) and contributes to neurodegeneration. This process can be studied in vivo with PET and radioligands targeting TSPO, upregulated in activated microglia. Initial PET studies investigating microglial activation in PD with the [ 11 C]-PK11195 have provided inconclusive results. Here we assess the presence and distribution of neuroinflammatory response in PD patients using [ 18 F]-DPA714 and to correlate imaging biomarkers to dopamine transporter imaging and clinical status., Methods: PD patients (n = 24, Hoehn and Yahr I-III) and 28 healthy controls were scanned with [ 18 F]-DPA714 and [ 11 C]-PE2I and analyzed. They were all genotyped for TSPO polymorphism. Regional binding parameters were estimated (reference Logan graphical approach with supervised cluster analysis). Impact of TSPO genotype was analyzed using Wilcoxon signed-rank test. Differences between groups were investigated using a two-way ANOVA and Tukey post hoc tests., Results: PD patients showed significantly higher [ 18 F]-DPA714 binding compared to healthy controls bilaterally in the midbrain (p < 0.001), the frontal cortex (p = 0.001), and the putamen contralateral to the more clinically affected hemibody (p = 0.038). Microglial activation in these regions did not correlate with the severity of motor symptoms, disease duration nor putaminal [ 11 C]-PE2I uptake. However, there was a trend toward a correlation between cortical TSPO binding and disease duration (p = 0.015 uncorrected, p = 0.07 after Bonferroni correction)., Conclusion: [ 18 F]-DPA714 binding confirmed that there is a specific topographic pattern of microglial activation in the nigro-striatal pathway and the frontal cortex of PD patients., Trial Registration: Trial registration: INFLAPARK, NCT02319382. Registered 18 December 2014- Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT02319382., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: The muscarinic receptor antagonist trospium chloride (TCl) is used for pharmacotherapy of the overactive bladder syndrome. TCl is a hydrophilic positively charged drug. Therefore, it has low permeability through biomembranes and requires drug transporters for distribution and excretion. In humans, the organic cation transporters OCT1 and OCT2 and the multidrug and toxin extrusion MATE1 and MATE2-K carriers showed TCl transport. However, their individual role for distribution and excretion of TCl is unclear. Knockout mouse models lacking mOct1/mOct2 or mMate1 might help to clarify their role for the overall pharmacokinetics of TCl., Method: In preparation of such experiments, TCl transport was analyzed in HEK293 cells stably transfected with the mouse carriers mOct1, mOct2, mMate1, and mMate2, respectively., Results: Mouse mOct1, mOct2, and mMate1 showed significant TCl transport with Km values of 58.7, 78.5, and 29.3 µM, respectively. In contrast, mMate2 did not transport TCl but showed MPP + transport with Km of 60.0 µM that was inhibited by the drugs topotecan, acyclovir, and levofloxacin., Conclusion: TCl transport behavior as well as expression pattern were quite similar for the mouse carriers mOct1, mOct2, and mMate1 compared to their human counterparts.

Dopaminergic (DA) system function is frequently disrupted after traumatic brain injury (TBI). However, published interventions that target the DA system with the hope of enhancing functional outcomes are inconclusive, partially because of the lack of DA signaling biomarkers that can be used to select patients likely to benefit from DA-directed therapies or to monitor treatment efficacy. The aim of this study was to evaluate the feasibility of using 123 I-iofluopane single-photon emission computerized tomography (SPECT) to assess pre-synaptic DA system dysfunction after severe TBI. Eighteen patients with severe TBI were enrolled in this study. 123 I-iofluopane SPECT imaging was performed at baseline and again 2.5 h after a single dose of methylphenidate (MP) administered enterally. DA transporter (DAT) specific binding ratio (SBR) before and after MP was measured. Functional outcomes included the Disability Rating Scale, JFK Coma Recovery Scale-Revised, Functional Independence Measure, and Functional Assessment Measure. Thirteen of 18 patients completed the study. Average time from injury to SPECT scan was 48 days (standard deviation [SD], 24 days; median, 31). Baseline ioflupane striatal SBR was 1.51 ± 0.46 (median, 1.67). A 43.1% (SD, 16; median, 46.5) displacement of ioflupane from pre-synaptic DAT was observed after MP administration. Baseline SBR positively correlated with functional status at baseline and 4 weeks after completion of the study. Serum MP levels correlated with relative change in SBR ( r s  = 0.60; p  = 0.04). Our findings suggest that 123 I-iofluopane SPECT is a promising tool to determine the severity of pre-synaptic DA terminal disruption and for monitoring pharmacokinetics and pharmacodynamics of therapeutic interventions targeting the DA system.

Aim: Dysfunction of dopaminergic neurons in the central nervous system is considered to be related to major depressive disorder (MDD). Especially, MDD in geriatric patients is characterized by anhedonia, which is assumed to be associated with reduced dopamine neurotransmission in the reward system. Dopamine transporter (DAT) is considered to reflect the function of the dopamine nerve system. However, previous DAT imaging studies using single photon emission computed tomography or positron emission tomography (PET) have shown inconsistent results. The radioligand [ 18 F]FE-PE2I for PET enables more precise evaluation of DAT availability. Hence, we aimed to evaluate the DAT availability in geriatric patients with MDD using [ 18 F]FE-PE2I., Methods: Eleven geriatric patients with severe MDD and 27 healthy controls underwent PET with [ 18 F]FE-PE2I, which has high affinity and selectivity for DAT. Binding potentials (BP ND ) in the striatum (caudate and putamen), nucleus accumbens (NAc), and substantia nigra were calculated. BP ND values were compared between MDD patients and healthy controls., Results: MDD patients showed significantly lower DAT BP ND in the NAc (P = 0.009), and there was a trend of lower BP ND in the putamen (P = 0.032) compared to controls., Conclusion: We found low DAT in the NAc and putamen in geriatric patients with severe MDD, which could be related to dysregulation of the reward system., (© 2020 The Authors Psychiatry and Clinical Neurosciences © 2020 Japanese Society of Psychiatry and Neurology.)

Trospium chloride, a muscarinic receptor blocker, is poorly absorbed with different rates from areas in the jejunum and the cecum/ascending colon. To evaluate whether organic cation transporter (OCT) 1, OCT2 and multidrug and toxin extrusion (MATE) 1 and MATE2-K are involved in pharmacokinetics, competitions with ranitidine, a probe inhibitor of the cation transporters, were evaluated in transfected HEK293 cells. Furthermore, a drug interaction study with trospium chloride after intravenous (2 mg) and oral dosing (30 mg) plus ranitidine (300 mg) was performed in 12 healthy subjects and evaluated by noncompartmental analysis and population pharmacokinetic modeling. Ranitidine inhibited OCT1, OCT2, MATE1, and MATE2-K with half maximal inhibitory concentration values of 186 ± 25 µM, 482 ± 105 µM, 134 ± 37 µM, and 35 ± 11 µM, respectively. In contrast to our hypothesis, coadministration of ranitidine did not significantly decrease oral absorption of trospium. Instead, renal clearance was lowered by ∼15% (530 ± 99 vs 460 ± 120 mL/min; P < .05). It is possible that ranitidine was not available in competitive concentrations at the major colonic absorption site, as the inhibitor is absorbed in the small intestine and undergoes degradation by microbiota. The renal effects apparently result from inhibition of MATE1 and/or MATE2-K by ranitidine as predicted by in vitro to in vivo extrapolation. However, all pharmacokinetic changes were not of clinical relevance for the drug with highly variable pharmacokinetics. Intravenous trospium significantly lowered mean absorption time and relative bioavailability of ranitidine, which was most likely caused by muscarinic receptor blocking effects on intestinal motility and water turnover., (© 2019 The Authors. The Journal of Clinical Pharmacology published by Wiley Periodicals, Inc. on behalf of American College of Clinical Pharmacology.)

The quaternary ammonium compound trospium chloride is poorly absorbed from 2 "absorption windows" in the jejunum and cecum/ascending colon, respectively. To confirm whether intestinal P-glycoprotein (P-gp) is involved, a 4-period, crossover drug interaction study with trospium chloride after intravenous (2 mg) and oral administration (30 mg) without and after comedication of clarithromycin (500 mg), an inhibitor for P-gp, was initiated in 12 healthy subjects. Pharmacokinetics of trospium was evaluated using gas chromatography-mass spectrometry, noncompartmental evaluation, and pharmacokinetic modeling. Trospium chloride was poorly absorbed after oral administration (absolute bioavailability, ∼8%-10%). About 30% of the bioavailable dose fraction was absorbed from the "narrow window". Comedication with clarithromycin increased steady-state distribution volumes by ∼27% (P < .01). Bioavailability was not increased as hypothesized. The geometric mean ratios (90% confidence interval) for area under the plasma concentration-time curve, maximum concentration, and renal clearance accounted for 0.75 (0.56-1.01), 0.64 (0.45-0.89), and 1.00 (0.90-1.13), respectively. The amount of trospium absorbed from the "narrow window" was reduced in all subjects but from the "wider window" in only 9 of them. Bioavailability was strongly predicted by the maximum absorption rate of trospium in the distal "window" (rs 2  = 0.910, P < .0001). In conclusion, the P-gp inhibitor clarithromycin significantly increases distribution volumes but not oral absorption of trospium. The amount absorbed from the "narrow window" was lowered in all subjects. However, the extent of all influences seems not to be of clinical relevance., (© 2019, The American College of Clinical Pharmacology.)

Food induced viscosity in the gastrointestinal tract is reported to reduce the bioavailability of tablets containing BCS class 3 drugs, mainly by retarding their disintegration and dissolution of the active pharmaceutical ingredient. The role of formulation factors in minimizing this negative food effect is largely unknown. Combinations of disintegrants were studied together with soluble and insoluble fillers and trospium chloride as model drug substance. Different batches of tablets were compressed at 10 kN and 30 kN, by incorporating different combinations of croscarmellose sodium (CSS), cross-linked (CPD) and sodium starch glycolate (SSG) at low level i.e, 2% + 2% and high level i.e, 4% + 4% of compressional weight, while taking lactose as a soluble filler and dibasic calcium phosphate (DCP) and microcrystalline cellulose (MCC) as insoluble fillers. Under low viscous conditions, disintegration of DCP based tablets was faster compared to lactose based tablets, but under high viscous conditions, simulating the effect of an ingested FDA meal, the disintegration behavior was reverted. Increased compressional force prolonged the disintegration of lactose and DCP based formulations under fasted conditions. However, when evaluated under food viscosity conditions, DCP based tablets compressed at higher force showed rapid disintegration while no effect of increased compressional force in lactose based tablets was observed. MCC based tablets in particular showed largely prolonged disintegration times in viscous media irrespective of the disintegrant type and levels investigated. Disintegrant combinations possessing wicking ability with minimum or no gelling were found to reduce disintegration times. The disintegrant combination of CPD + CCS was effective in reducing disintegration and enhancing dissolution besides not being affected by changes in compressional force and their total proportion in the tablet. In conclusion, it is recommended to evaluate formulations under increased viscosity conditions during the development phase of tablets with an objective to minimize the negative effect of food viscosity on disintegration and dissolution., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Introduction: Discrete patterns of progression have been suggested for patients with Parkinson disease and presenting tremor dominant (TD) or postural instability gait disorders (PIGD). However, longitudinal prospective assessments need to take into consideration the variability in clinical manifestations and the evidence that only 40% of initially classified PIGD remain in this subtype at subsequent visits., Methods: We analyzed clinical progression of PIGD compared to TD using longitudinal clinical data from the PPMI. Given the reported instability of such clinical classification, we only included patients who were reported as PIGD/TD at each visit during the 4-year observation. We used linear mixed-effects models to test differences in progression in these subgroups in 51 dependent variables., Results: There were 254 patients with yearly assessment. The number of PIGD was 36/254 vs 144/254 TD. PIGD had more severe motor disease at baseline but progressed faster than TD only in three non-motor items of the MDS-UPDRS: cognitive impairment, hallucinations, and psychosis plus features of DDS. Our analysis also showed in PIGD faster increase in the average time with dyskinesia., Conclusions: PIGD are characterized by more severe disease manifestations at diagnosis and greater cognitive progression, more frequent hallucinations, psychosis as well as features of DDS than TD patients. We interpret these findings as expression of greater cortical and subcortical involvement in PIGD already at onset. Since PIGD/TD classification is very unstable at onset, our analysis based on stricter definition criteria provides important insight for clinical trial stratification and definition of related outcome measures.

We examined the correlations between cerebrospinal fluid (CSF) concentrations of homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA) and imaging assessment scores, using 123 I-Ioflupane SPECT and 123 I-MIBG myocardial scintigraphy in 23 drug naïve PD patients. The CSF 5-HIAA concentration correlated with the H/M ratio of the delayed image (r = 0.458, p < 0.05) and the washout rate (r = - 0.642, p < 0.01) of 123 I-MIBG myocardial scintigraphy. These correlations suggest some unclarified pathophysiological links between the central serotonergic and cardiac sympathetic systems.

18 F-( E )- N -(3-iodoprop-2-enyl)-2β-carbofluoroethoxy-3β-(4'-methyl-phenyl) nortropane ( 18 F-FE-PE2I) was recently developed and has shown adequate affinity and high selectivity for the dopamine transporter (DAT). Previous studies have shown promising results for 18 F-FE-PE2I as a suitable radioligand for DAT imaging. In this study, we investigated the whole-body biodistribution and dosimetry of 18 F-FE-PE2I in healthy volunteers to support its utility as a suitable PET imaging agent for the DAT. Methods: Five healthy volunteers were given a mean activity of 2.5 MBq/kg, and 3 PET scans, head to thigh, were performed immediately after injection followed by 4 whole-body PET/CT scans between 0.5 and 6 h after injection. Blood samples were drawn in connection with the whole-body scans, and all urine was collected until 6 h after injection. Volumes of interest were delineated around 17 organs on all images, and the areas under the time-activity curves were calculated to obtain the total number of decays in the organs. The absorbed doses to organs and the effective dose were calculated using the software IDAC. Results: The highest activity concentration was observed in the liver (0.9%-1.2% injected activity/100 g) up to 30 min after injection. At later time points, the highest concentration was seen in the gallbladder (1.1%-0.1% injected activity/100 g). The activity excreted with urine ranged between 23% and 34%, with a mean of 28%. The urinary bladder received the highest absorbed dose (119 μGy/MBq), followed by the liver (46 μGy/MBq). The effective dose was 23 μSv/MBq (range, 19-28 μSv/MBq), resulting in an effective dose of 4.6 mSv for an administered activity of 200 MBq. Conclusion: The effective dose is within the same order of magnitude as other commonly used PET imaging agents as well as DAT agents. The reasonable effective dose, together with the previously reported favorable characteristics for DAT imaging and quantification, indicates that 18 F-FE-PE2I is a suitable radioligand for DAT imaging., (© 2018 by the Society of Nuclear Medicine and Molecular Imaging.)

Objective: The objective of this study was to assess longitudinal change in clinical and dopamine transporter imaging outcomes in early, untreated PD., Methods: We describe 5-year longitudinal change of the MDS-UPDRS and other clinical measures using results from the Parkinson's Progression Markers Initiative, a longitudinal cohort study of early Parkinson's disease (PD) participants untreated at baseline. We also provide data on the longitudinal change in dopamine transporter 123-I Ioflupane striatal binding and correlation between the 2 measures., Results: A total of 423 PD participants were recruited, and 358 remain in the study at year 5. Baseline MDS-UPDRS total score was 32.4 (standard deviation 13.1), and the average annual change (assessed medications OFF for the treated participants) was 7.45 (11.6), 3.11 (11.7), 4(11.9), 4.7 (11.1), and 1.74(11.9) for years 1, 2, 3, 4, and 5, respectively (P < .0001 for the change over time), with a steeper change in year 1. Dopaminergic therapy had a significant effect on the change of MDS-UPDRS. There was a significant longitudinal change in dopamine transporter binding in all striatal regions (P < .001). There was a significant but weak correlation between MDS-UPDRS and dopamine transporter binding at baseline and years 1, 2, and 4, but no correlation between the rate of change of the 2 variables., Conclusions: We present 5-year longitudinal data on the change of the MDS-UPDRS and other clinical and dopamine transporter imaging outcome measures in early PD. These data can be used for sample size estimates for interventional studies in the de novo PD population. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society., (© 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.)

Traumatic brain injury can reduce striatal dopamine levels. The cause of this is uncertain, but is likely to be related to damage to the nigrostriatal system. We investigated the pattern of striatal dopamine abnormalities using 123I-Ioflupane single-photon emission computed tomography (SPECT) scans and their relationship to nigrostriatal damage and clinical features. We studied 42 moderate-severe traumatic brain injury patients with cognitive impairments but no motor parkinsonism signs and 20 healthy controls. 123I-Ioflupane scanning was used to assess dopamine transporter levels. Clinical scan reports were compared to quantitative dopamine transporter results. Advanced MRI methods were used to assess the nigrostriatal system, including the area through which the nigrostriatal projections pass as defined from high-resolution Human Connectome data. Detailed clinical and neuropsychological assessments were performed. Around 20% of our moderate-severe patients had clear evidence of reduced specific binding ratios for the dopamine transporter in the striatum measured using 123I-Ioflupane SPECT. The caudate was affected more consistently than other striatal regions. Dopamine transporter abnormalities were associated with reduced substantia nigra volume. In addition, diffusion MRI provided evidence of damage to the regions through which the nigrostriatal tract passes, particularly the area traversed by dopaminergic projections to the caudate. Only a small percentage of patients had evidence of macroscopic lesions in the striatum and there was no relationship between presence of lesions and dopamine transporter specific binding ratio abnormalities. There was also no relationship between reduced volume in the striatal subregions and reduced dopamine transporter specific binding ratios. Patients with low caudate dopamine transporter specific binding ratios show impaired processing speed and executive dysfunction compared to patients with normal levels. Taken together, our results suggest that the dopaminergic system is affected by a moderate-severe traumatic brain injury in a significant proportion of patients, even in the absence of clinical motor parkinsonism. Reduced dopamine transporter levels are most commonly seen in the caudate and this is likely to reflect the pattern of nigrostriatal tract damage produced by axonal injury and associated midbrain damage.

Background: 18 F-dopa PET measuring aromatic l-amino acid decarboxylase activity is regarded as the gold standard for evaluating dopaminergic function in Parkinson's disease. Radioligands for dopamine transporters are also used in clinical trials and for confirming PD diagnosis. Currently, it is not clear which imaging marker is more reliable for assessing clinical severity and rate of progression. The objective of this study was to directly compare 18 F-dopa with the highly selective dopamine transporter radioligand 11 C-PE2I for the assessment of motor severity and rate of progression in PD., Methods: Thirty-three mild-moderate PD patients underwent 18 F-dopa and 11 C-PE2I PET at baseline. Twenty-three were followed up for 18.8 ± 3.4 months., Results: Standard multiple regression at baseline indicated that 11 C-PE2I BP ND predicted UPDRS-III and bradykinesia-rigidity scores (P < 0.05), whereas 18 F-dopa K i did not make significant unique explanatory contributions. Voxel-wise analysis showed negative correlations between 11 C-PE2I BP ND and motor severity across the whole striatum bilaterally. 18 F-Dopa K i clusters were restricted to the most affected putamen and caudate. Longitudinally, negative correlations were found between striatal Δ 11 C-PE2I BP ND , ΔUPDRS-III, and Δbradykinesia-rigidity, whereas no significant associations were found for Δ 18 F-dopa K i . One cluster in the most affected putamen was identified in the longitudinal voxel-wise analysis showing a negative relationship between Δ 11 C-PE2I BP ND and Δbradykinesia-rigidity., Conclusions: Striatal 11 C-PE2I appears to show greater sensitivity for detecting differences in motor severity than 18 F-dopa. Furthermore, dopamine transporter decline is closely associated with motor progression over time, whereas no such relationship was found with aromatic l-amino acid decarboxylase. 11 C-PE2I may be more effective for evaluating the efficacy of neuroprotective treatments in PD. © 2017 International Parkinson and Movement Disorder Society., (© 2017 International Parkinson and Movement Disorder Society.)

It is reported that pharmacokinetics after intravenous injection of 123 I-ioflupane may reflect cerebral blood flow. In this study, the early-phase pharmacokinetics of 123 I-ioflupane in 10 healthy volunteers was analyzed over time using dynamic single-photon emission computed tomography (SPECT) immediately after intravenous injection. We also examined the correlation between the 123 I-IMP imaging and the 123 I-ioflupane early-phase image for 14 cases in which both dopamine transporter (DaT) imaging by 123 I-ioflupane and cerebral blood flow imaging by 123 I-IMP were performed on the same camera. The time-activity curve between cerebellum (CBL) area and each area of anterior cerebral artery (ACA), middle cerebral artery (MCA), posterior cerebral artery (PCA) showed distribution characteristics similar to 123 I-IMP from immediately after intravenous injection until 20 minutes after administration, and there was no conspicuous washout. The regression line and the correlation coefficient of the Z-score of three-dimensional stereotactic surface projections (3DSSP) (decrease) of the early-phase imaging of 123 I-ioflupane and the 123 I-IMP imaging are y=0.7546x+0.3562, r=0.8169 (P<0.01) at 0-10 minutes of 123 I-ioflupane, and y=0.7412x+0.3027, r=0.8280 (P<0.01) at 0-15 minutes of 123 I-ioflupane, and y=0.7400x+0.2456, r=0.8449 (P<0.01) at 0-20 minutes of 123 I-ioflupane, showing a strong correlation at all timings. Therefore, 123 I-ioflupane early-phase pharmacokinetics after intravenous showed distribution characteristics similar to 123 I-IMP, indicating the possibility that early images may be useful in a clinical practice.

Mutations in XPR1, a gene encoding an inorganic phosphate exporter, have recently been identified in patients with primary familial brain calcification (PFBC). Using Sanger sequencing, we screened XPR1 in 18 unrelated patients with PFBC and no SLC20A2, PDGFB, or PDGFRB mutation. XPR1 variants were tested in an in vitro physiological complementation assay and patient blood cells were assessed ex vivo for phosphate export. We identified a novel c.260T > C, p.(Leu87Pro) XPR1 variant in a 41-year-old man complaining of micrographia and dysarthria and demonstrating mild parkinsonism, cerebellar ataxia and executive dysfunction. Brain (123)I-Ioflupane scintigraphy showed marked dopaminergic neuron loss. Peripheral blood cells from the patient exhibited decreased phosphate export. XPR1 in which we introduced the mutation was not detectable at the cell surface and did not lead to phosphate export. These results confirm that loss of XPR1-mediated phosphate export function causes PFBC, occurring in less than 8 % of cases negative for the other genes, and may be responsible for parkinsonism.

Dopamine transporter (DAT) SPECT imaging is increasingly utilized for diagnostic purposes in suspected Parkinsonian syndromes. We performed a cross-sectional study to investigate whether assessment of texture in DAT SPECT radiotracer uptake enables enhanced correlations with severity of motor and cognitive symptoms in Parkinson's disease (PD), with the long-term goal of enabling clinical utility of DAT SPECT imaging, beyond standard diagnostic tasks, to tracking of progression in PD. Quantitative analysis in routine DAT SPECT imaging, if performed at all, has been restricted to assessment of mean regional uptake. We applied a framework wherein textural features were extracted from the images. Notably, the framework did not require registration to a common template, and worked in the subject-native space. Image analysis included registration of SPECT images onto corresponding MRI images, automatic region-of-interest (ROI) extraction on the MRI images, followed by computation of Haralick texture features. We analyzed 141 subjects from the Parkinson's Progressive Marker Initiative (PPMI) database, including 85 PD and 56 healthy controls (HC) (baseline scans with accompanying 3 T MRI images). We performed univariate and multivariate regression analyses between the quantitative metrics and different clinical measures, namely (i) the UPDRS (part III - motor) score, disease duration as measured from (ii) time of diagnosis (DD-diag.) and (iii) time of appearance of symptoms (DD-sympt.), as well as (iv) the Montreal Cognitive Assessment (MoCA) score. For conventional mean uptake analysis in the putamen, we showed significant correlations with clinical measures only when both HC and PD were included (Pearson correlation r  = - 0.74, p-value < 0.001). However, this was not significant when applied to PD subjects only ( r  = - 0.19, p-value = 0.084), and no such correlations were observed in the caudate. By contrast, for the PD subjects, significant correlations were observed in the caudate when including texture metrics, with (i) UPDRS (p-values < 0.01), (ii) DD-diag. (p-values < 0.001), (iii) DD-sympt (p-values < 0.05), and (iv) MoCA (p-values < 0.01), while no correlations were observed for conventional analysis (p-values = 0.94, 0.34, 0.88 and 0.96, respectively). Our results demonstrated the ability to capture valuable information using advanced texture metrics from striatal DAT SPECT, enabling significant correlations of striatal DAT binding with clinical, motor and cognitive outcomes, and suggesting that textural features hold potential as biomarkers of PD severity and progression.

There are a number of clinical questions for which there are no easy answers, even for well-trained doctors. The diagnostic tool commonly used to assess cognitive impairment in neurodegenerative diseases is based on established clinical criteria. However, the differential diagnosis between disorders can be difficult, especially in early phases or atypical variants. This takes on particular importance when it is still possible to use an appropriate treatment. To solve this problem, physicians need to have access to an arsenal of diagnostic tests, such as neurofunctional imaging, that allow higher specificity in clinical assessment. However, the reliability of diagnostic tests may vary from one to the next, so the diagnostic validity of a given investigation must be estimated by comparing the results obtained from "true" criteria to the "gold standard" or reference test. While pathological analysis is considered to be the gold standard in a wide spectrum of diseases, it cannot be applied to neurological processes. Other approaches could provide solutions, including clinical patient follow-up, creation of a data bank or use of computer-aided diagnostic algorithms. In this article, we discuss the development of different methodological procedures related to analysis of diagnostic validity and present an example from our own experience based on the use of I-123-ioflupane-SPECT in the study of patients with movement disorders. The aim of this chapter is to approach the problem of diagnosis from the point of view of the clinician, taking into account specific aspects of neurodegenerative disease.

The cationic, water-soluble quaternary trospium chloride (TC) is incompletely absorbed from the gut and undergoes wide distribution but does not pass the blood-brain barrier. It is secreted by the kidneys, liver, and intestine. To evaluate potential transport mechanisms for TC, we measured affinity of the drug to the human uptake and efflux transporters known to be of pharmacokinetic relevance. Affinity of TC to the uptake transporters OATP1A2, -1B1, -1B3, -2B1, OCT1, -2, -3, OCTN2, NTCP, and ASBT and the efflux carriers P-gp, MRP2 and MRP3 transfected in HEK293 and MDCK2 cells was measured. To identify relevant pharmacokinetic mechanisms in the bladder urothelium, mRNA expression of multidrug transporters, drug metabolizing enzymes, and nuclear receptors, and the uptake of TC into primary human bladder urothelium (HBU) cells were measured. TC was shown to be a substrate of OATP1A2 (Km = 6.9 ± 1.3 μmol/L; Vmax = 41.6 ± 1.8 pmol/mg·min), OCT1 (Km = 106 ± 16 μmol/L; Vmax = 269 ± 18 pmol/mg·min), and P-gp (Km = 34.9 ± 7.5 μmol/L; Vmax = 105 ± 9.1 pmol/mg·min, lipovesicle assay). The genetic OATP1A2 variants *2 and *3 were loss-of-function transporters for TC. The mRNA expression analysis identified the following transporter proteins in the human urothelium: ABCB1 (P-gp), ABCC1-5 (MRP1-5), ABCG2 (BCRP), SLCO2B1 (OATP2B1), SLCO4A1 (OATP4A1), SLC22A1 (OCT1), SLC22A3 (OCT3), SLC22A4 (OCTN1), SLC22A5 (OCTN2), and SLC47A1 (MATE1). Immuno-reactive P-gp and OATP1A2 were localized to the apical cell layers. Drug metabolizing enzymes CYP3A5, -2B6, -2B7 -2E1, SULT1A1-4, UGT1A1-10, and UGT2B15, and nuclear receptors NR1H3 and NR1H4 were also expressed on mRNA level. TC was taken up into HBU cells (Km = 18.5 ± 4.8 μmol/L; Vmax = 106 ± 11.3 pmol/mg·min) by mechanisms that could be synergistically inhibited by naringin (IC50 = 10.8 (8.4; 13.8) μmol/L) and verapamil (IC50 = 4.6 (2.8; 7.5) μmol/L), inhibitors of OATP1A2 and OCT1, respectively. Affinity of TC to OCT1 and P-glycoprotein may be the reason for incomplete oral absorption, wide distribution into liver and kidneys, and substantial intestinal and renal secretions. Absence of brain distribution may result from affinity to P-gp and a low affinity to OATP1A2. The human urothelium expresses many drug transporters and drug metabolizing enzymes that may interact with TC and other drugs eliminated into the urine.

The purpose of this study was to mechanistically interpret the oral absorption pattern of trospium in fasted and fed states by means of gastrointestinal simulation technology. A drug absorption model was built on the basis of experimental data. According to the generated model, low permeability across the intestinal epithelium, delayed gastric emptying time and a prolonged residence time in the small intestine are the key factors governing trospium absorption in the fasted state. Furthermore, in silico modelling provided a plausible explanation of the pronounced reduction in the oral bioavailability of trospium when administered with food. The simulation results support the decreased dissolution in viscous medium, and the reduced drug permeability in the fed state as the predominant mechanisms for the food effect on trospium absorption., (Copyright © 2014 John Wiley & Sons, Ltd.)

The delayed appearance of motor symptoms in PD poses a crucial challenge for early detection of the disease. We measured the binding potential of the selective dopamine active transporter (DAT) radiotracer [(11)C]PE2I in MPTP-treated macaque monkeys, thus establishing a detailed profile of the nigrostriatal DA status following MPTP intoxication and its relation to induced motor and non-motor symptoms. Clinical score and cognitive performance were followed throughout the study. We measured longitudinally in vivo the non-displaceable binding potential to DAT in premotor, motor-recovered (i.e. both non-symptomatic) and symptomatic MPTP-treated monkeys. Results show an unexpected and pronounced dissociation between clinical scores and [(11)C]PE2I-BP(ND) during the premotor phase i.e. DAT binding in the striatum of premotor animals was increased around 20%. Importantly, this broad increase of DAT binding in the caudate, ventral striatum and anterior putamen was accompanied by i) deteriorated cognitive performance, showing a likely causal role of the observed hyperdopaminergic state (Cools, 2011; Cools and D'Esposito, 2011) and ii) an asymmetric decrease of DAT binding at a focal point of the posterior putamen, suggesting that increased DAT is one of the earliest, intrinsic compensatory mechanisms. Following spontaneous recovery from motor deficits, DAT binding was greatly reduced as recently shown in-vivo with other radiotracers (Blesa et al., 2010, 2012). Finally, high clinical scores were correlated to considerably low levels of DAT only after the induction of a stable parkinsonian state. We additionally show that the only striatal region which was significantly correlated to the degree of motor impairments is the ventral striatum. Further research on this period should allow better understanding of DA compensation at premature stages of PD and potentially identify new diagnosis and therapeutic index., (Copyright © 2014. Published by Elsevier Inc.)

In the current study the involvement of ion pair formation between bile salts and trospium chloride (TC), a positively charged Biopharmaceutical Classification System (BCS) class III substance, showing a decrease in bioavailability upon coadministration with food (negative food effect) was investigated. Isothermal titration calorimetry provided evidence of a reaction between TC and bile acids. An effect of ion pair formation on the apparent partition coefficient (APC) was examined using (3)H-trospium. The addition of bovine bile and bile extract porcine led to a significant increase of the APC. In vitro permeability studies of trospium were performed across Caco-2-monolayers and excised segments of rat jejunum in a modified Ussing chamber. The addition of bile acids led to an increase of trospium permeation across Caco-2-monolayers and rat excised segments by approximately a factor of 1.5. The addition of glycochenodeoxycholate (GCDC) was less effective than taurodeoxycholate (TDOC). In the presence of an olive oil emulsion, a complete extinction of the permeation increasing effects of bile salts was observed. Thus, although there are more bile acids in the intestine in the fed state compared to the fasted state, these are not able to form ion pairs with trospium in fed state, because they are involved in the emulsification of dietary fats. In conclusion, the formation of ion pairs between trospium and bile acids can partially explain its negative food effect. Our results are presumably transferable to other organic cations showing a negative food effect.

The objective of this study was to investigate the potential of λ-carrageenan to work as an absorption modifying excipient in combination with formulations of BCS class 3 substances. Trospium chloride was used as a model BCS class 3 substance. Polyelectrolyte complexes of trospium and λ-carrageenan were produced by layer-by-layer complexation. A λ-carrageenan-containing formulation was administered either in capsules size 9 to rats by gavage or directly into ligated intestinal loops of rats. Exceptionally strong variations were observed in the plasma concentrations of the rats that received λ-carrageenan compared to the control group, but enhanced plasma concentrations were observed only in some of the rats. In vitro permeability studies were performed across Caco2-monolayers and across excised segments of rat jejunum in a modified Ussing chamber to learn more about the mechanism of absorption enhancement. The complex did not show any effect in Caco2-cells, but led to a major enhancement of permeability across excised segments in modified Ussing chambers. Carrageenan did not lead to alterations of tight junctions. The bioavailability enhancing effect thus was most likely due to an interaction of the polyelectrolyte-drug complex with the mucus, which provided an intimate contact between the drug and the absorbing surface. A similar effect was also achievable with other types of carrageenan and was also transferable to other compounds. In conclusion, λ-carrageenan-drug complexes show interesting excipient-drug-epithelium interactions - however, for full utilization of the permeation enhancing potential, an intimate and reproducible contact between absorbing epithelia and the complex is needed., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Unlabelled: Patients who have dementia with Lewy bodies (DLB) show both clinical and histopathologic overlap with Alzheimer disease patients and Parkinson disease patients. In this study, we correlated the core features of DLB (dementia, parkinsonism, hallucinations, and fluctuations) with striatal dopamine transporter (DAT) availability as assessed with SPECT and (123)I-N-(3-iodoprop-2E-enyl)-2-β-carbomethoxy-3β-(4-methylphenyl) nortropane ((123)I-PE2I) in patients with newly diagnosed DLB., Methods: Two hundred eighty-eight patients were consecutively included in the study as they were referred for diagnostic SPECT scanning of DAT with (123)I-PE2I. Of those patients, 51 had, on the basis of clinical guideline criteria, a probable-DLB diagnosis at follow-up 16 ± 11.6 mo later. Before or on the day of the SPECT scan, DLB patients had a routine neurologic examination including Hoehn and Yahr grading and were cognitively evaluated with the Mini Mental State Examination., Results: There was no correlation between Mini Mental State Examination, Hoehn and Yahr score, fluctuations or hallucinations, and striatal DAT availability as measured with (123)I-PE2I and SPECT., Conclusion: In patients with newly diagnosed DLB, symptoms are not associated with a reduction in striatal DAT despite its firm involvement in DLB pathology.

Objective: To ascertain in a cross-sectional study whether substantia nigra (SN) echogenicity, olfaction, and dopamine transporter (DaT)-SPECT are reliable premotor biomarkers in a cohort of asymptomatic carriers of the LRRK2 G2019S mutation (AsG2019S+)., Methods: These biomarkers were evaluated in 49 AsG2019S+ patients, and we also studied olfaction and SN echogenicity in 29 patients with G2019S-associated Parkinson disease (PD-G2019S), 47 relatives who were noncarriers of the LRRK2 G2019S mutation (AsG2019S-), 50 patients with idiopathic Parkinson disease (iPD), and 50 community controls., Results: Eighty-five percent of unaffected mutation carriers (AsG2019S+) showed pathologic SN hyperechogenicity, with a similar proportion observed among both PD-G2019S and iPD cases, and 41% of AsG2019S- also showing increased SN echogenicity. The proportion of hyposmic individuals was not statistically different in patients with PD-G2019S (50%) and iPD (82%), but hyposmia was significantly less common in both AsG2019S+ (26%) and AsG2019S- (28%). In AsG2019S+ cases, reduced striatal uptake in DaT-SPECT was observed in 43.7%., Conclusions: Independently of age at examination, the most frequently altered premotor biomarker in LRRK2 G2019S-associated PD was SN hyperechogenicity, whereas abnormal DaT-SPECT predominated in older, unaffected mutation carriers.

Purpose: To analyse whether the permeability of the blood-brain barrier to the antimuscarinic drug trospium chloride is altered with ageing. This is a relevant question for elderly patients with overactive bladder syndrome who are treated with trospium chloride as the occurrence of adverse effects on the central nervous system (CNS) highly depends on the absolute drug concentration in the brain., Methods: Trospium chloride at 1 mg/kg was intravenously administered to adult, middle-aged, and aged mice at 6, 12, and 24 months of age, respectively, and the absolute drug concentrations in the brain were analysed after 2 h. Furthermore, mRNA expression levels of relevant markers of blood-brain barrier integrity (occludin, claudin-5, and the drug efflux carrier P-glycoprotein) were analysed in brain samples from adult and aged mice., Results: The absolute brain concentrations of the drug were identical in adult and middle-aged mice (13 ± 2 ng/g vs. 13 ± 2 ng/g) and were slightly, but significantly, lower in aged mice (8 ± 4 ng/g). The brain/plasma drug concentration ratios were not different between the age groups and demonstrated the generally low capability of trospium chloride in permeating the blood-brain barrier. Occludin, claudin-5, and P-glycoprotein showed identical mRNA expression levels in the brains of adult and aged mice., Conclusion: Based on our in vivo data in a mouse model, we conclude that trospium chloride permeation across the BBB is not increased in ageing per se, and therefore, the occurrence of adverse CNS drug effects is also not expected to increase with ageing.

Background: Overactive bladder is a common disorder that affects approximately 34 million adults in the United States. Anticholinergic (antimuscarinic) agents are the most widely used pharmacological option for overactive bladder., Objective: This study set out to identify and characterize the influence of a number of intrinsic characteristics on the pharmacokinetics of the anticholinergic agent trospium chloride (Sanctura(®)) 60 mg extended release (XR), and to evaluate the correlation between trospium chloride exposure and key efficacy and safety outcomes in subjects and patients., Study Design: Pharmacokinetic data were obtained from three studies in which a total of 349 subjects received trospium chloride XR for up to 12 weeks. Plasma trospium chloride concentration data were pooled and a population pharmacokinetic model was derived using non-linear mixed-effects modelling. Demographic factors were assessed for influence on the model. The correlation between trospium chloride exposure and key efficacy variables was evaluated. Correlations between exposure and safety outcomes were also assessed., Intervention: Trospium chloride XR 60 mg once daily for 10 days in healthy volunteers or trospium chloride 60 mg XR once daily for either 2 weeks or 12 weeks in patients with overactive bladder., Results: The best population pharmacokinetic model was determined to be a two-compartment model with zero-order release into the depot compartment and first-order absorption. Body surface area (BSA) was the only covariate to significantly (P < 0.05) impact trospium chloride 60 mg XR pharmacokinetics. Significant relationships (P < 0.05) were observed between exposure [maximum plasma concentration (C(max)) and the area under the plasma concentration-time curve from time zero to 24 h (AUC(24))] and efficacy outcomes in the <65-year age group for change in average number of voids/day, change in number of incontinence episodes, and change in urgency severity, and in the ≥65-year age group statistical significance (P < 0.05) was achieved for C(max), but not for AUC(24), for these same three efficacy measures. Statistically significant relationships (P < 0.004) were also observed between exposure and both dry mouth and constipation, with increased benefit and increased incidence of adverse events (AEs) associated with higher concentrations; the correlation coefficients were low against the aggregate of AEs of interest (0.19 for AUC(24) and 0.18 for C(max)), indicating only mild strength of association., Conclusion: This population pharmacokinetic analysis demonstrated that the only demographic characteristic associated with trospium chloride pharmacokinetics was BSA. Thus, treatment of most patients with overactive bladder with once-daily trospium chloride 60 mg XR should not require consideration of key intrinsic demographic parameters. Furthermore, while efficacy and tolerability outcomes were found to be correlated with trospium chloride exposure, the strength of the association was modest in this study.

Introduction: In vivo imaging of the serotonin transporter continues to be a valuable tool in drug development and in monitoring diseases that alter serotonergic function. The purposes of this study were to: 1) evaluate the test/retest reproducibility of [¹²³I] 2β-Carbomethoxy-3β-(3'-((Z)-2-iodoethenyl)phenyl)nortropane ([¹²³I]mZIENT); and 2) to assess displacement of [¹²³I]mZIENT following administration of SERT specific drugs., Methods: Six female baboons (Papio anubis) were scanned following i.v. administration of [¹²³I]mZIENT. The regional binding potential (BP(nd)) was determined using a simplified reference tissue model, with the cerebellum used as a reference region. The test/retest reproducibility of BP(nd) was determined following repeated injection of [¹²³I]mZIENT on a different day. To assess the displacement of [¹²³I]mZIENT from SERT, citalopram (0.01-5mg/kg) or sertraline (0.01-0.5mg/kg) was given as iv bolus at ~4h following administration of [¹²³I]mZIENT., Results: The test/retest variability of BP(nd) was less than 10% for all SERT-rich brain regions. Estimates of ED50 for displacement of [¹²³I]mZIENT in SERT-rich regions were consistent with previous reports for the [¹¹C] analog of [¹²³I]mZIENT. Both citalopram and sertraline displaced [¹²³I]mZIENT from SERT in a dose-dependent manner, with maximal observed displacements of greater than 80% in the diencephalon and greater than 75% in brainstem for both citalopram and sertraline., Conclusions: [¹²³I] mZIENT demonstrates good test-retest reproducibility; and initial displacement studies suggest that this compound is highly selective for SERT. Overall, this radioligand has favorable characteristics for use in drug development studies and/or longitudinal studies interrogating SERT., (Copyright © 2012 Elsevier Inc. All rights reserved.)

A negative food effect, i.e. a decrease in bioavailability upon the co-administration of compounds together with food, has been attributed particularly with high solubility/low permeability compounds (BCS class III). Different mechanisms have been proposed including intestinal dilution leading to a lower concentration gradient across the intestinal wall as well as binding of the active pharmaceutical ingredient to food components in the intestine and thereby decreasing the fraction of the dose available for absorption. These mechanisms refer primarily to the compound and not to the dosage form. An increase in viscosity of the dissolution fluid will in particular affect the absorption of BCS type III compounds with preferential absorption in the upper small intestine if the API release is delayed from the dosage form. The present study demonstrated that the increase in viscosity of the dissolution medium, following ingestion of a solid meal, may drastically reduce disintegration and dissolution. For that purpose the viscosity of the standard FDA meal was determined and simulated by solutions of HPMC in buffer. As model formulations, three commercially available tablets containing trospium chloride, a BCS class III m-cholinoreceptor antagonist was used. Trospium chloride drug products have been described to undergo a negative food effect of more than 80% following ingestion with food. The tablets showed prolonged disintegration times and reduced dissolution rates in viscous media, which could be attributed to changes in the liquid penetration rates. The effect was particularly significant for film-coated tablets relative to uncoated dosage forms. The results show the necessity of considering media viscosity when designing in vitro models of drug release for BCS type III drug formulations., (Copyright © 2012 John Wiley & Sons, Ltd.)

This study was aimed to investigate the potential neuroprotective effect of neuropeptide Y (NPY) on the survival of dopaminergic cells in both in vitro and in animal models of Parkinson's disease (PD). NPY protected human SH-SY5Y dopaminergic neuroblastoma cells from 6-hydroxydopamine-induced toxicity. In rat and mice models of PD, striatal injection of NPY preserved the nigrostriatal dopamine pathway from degeneration as evidenced by quantification of (1) tyrosine hydroxylase (TH)-positive cells in the substantia nigra pars compacta, levels of (2) striatal tyrosine hydroxylase and dopamine transporter, (3) dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) as well as (4) rotational behavior. NPY had no neuroprotective effects in mice treated with Y(2) receptor antagonist or in transgenic mice deficient for Y(2) receptor suggesting that NPY effects are mediated through this receptor. Stimulation of Y(2) receptor by NPY triggered the activation of both the ERK1/2 and Akt pathways but did not modify levels of brain derived neurotrophic factor (BDNF) or glial cell line-derived neurotrophic factor. These results open new perspectives in neuroprotective therapies using NPY and suggest potential beneficial effects in PD., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Unlabelled: (18)F-(E)-N-(3-iodoprop-2E-enyl)-2β-carbofluoroethoxy-3β-(4-methylphenyl)nortropane ((18)F-FE-PE2I) is a new PET radioligand with a high affinity and selectivity for the dopamine transporter (DAT). In nonhuman primates, (18)F-FE-PE2I showed faster kinetics and less production of radiometabolites that could potentially permeate the blood-brain barrier than did (11)C-PE2I. The aims of this study were to examine the quantification of DAT using (18)F-FE-PE2I and to assess the effect of radiometabolites of (18)F-FE-PE2I on the quantification in healthy humans., Methods: A 90-min dynamic PET scan was obtained for 10 healthy men after intravenous injection of (18)F-FE-PE2I. Kinetic compartment model analysis with a metabolite-corrected arterial input function was performed. The effect of radiometabolites on the quantification was evaluated by time-stability analyses. The simplified reference tissue model (SRTM) method with the cerebellum as a reference region was evaluated as a noninvasive method of quantification., Results: After the injection of (18)F-FE-PE2I, the whole-brain radioactivity showed a high peak (∼3-5 standardized uptake value) and fast washout. The radioactive uptake of (18)F-FE-PE2I in the brain was according to the relative density of the DAT (striatum > midbrain > thalamus). The cerebellum showed the lowest uptake. Tissue time-activity curves were well described by the 2-tissue-compartment model (TCM), as compared with the 1-TCM, for all subjects in all regions. Time stability analysis showed stable estimation of total distribution volume with 60-min or longer scan durations, indicating the small effect of radiometabolites. Binding potentials in the striatum and midbrain were well estimated by the SRTM method, with modest intersubject variability. Although the SRTM method yielded a slight underestimation and overestimation in regions with high and low DAT densities, respectively, binding potentials by the SRTM method were well correlated to the estimates by the indirect kinetic method with 2-TCM., Conclusion: (18)F-FE-PE2I is a promising PET radioligand for quantifying DAT. The binding potentials could be reliably estimated in both the striatum and midbrain using both the indirect kinetic and SRTM methods with a scan duration of 60 min. Although radiometabolites of (18)F-FE-PE2I in plasma possibly introduced some effects on the radioactivity in the brain, the effects on estimated binding potential were likely to be small.

Purpose: 123I-labelled mZIENT (2β-carbomethoxy-3β-(3′-((Z)-2-iodoethenyl)phenyl)nortropane) has been developed as a radioligand for the serotonin transporter. The aim of this preliminary study was to assess its whole-body biodistribution in humans and estimate dosimetry., Methods: Three healthy controls and three patients receiving selective serotonin reuptake inhibitor (SSRI) therapy for depression were included (two men, four women, age range 41-56 years). Whole-body imaging, brain SPECT imaging and blood and urine sampling were performed. Whole-body images were analysed using regions of interest (ROIs), time-activity curves were derived using compartmental analysis and dosimetry estimated using OLINDA software. Brain ROI analysis was performed to obtain specific-to-nonspecific binding ratios in the midbrain, thalamus and striatum., Results: Initial high uptake in the lungs decreased in later images. Lower uptake was seen in the brain, liver and intestines. Excretion was primarily through the urinary system. The effective dose was estimated to be of the order of 0.03 mSv/MBq. The organ receiving the highest absorbed dose was the lower large intestine wall. Uptake in the brain was consistent with the known SERT distribution with higher specific-to-nonspecific binding in the midbrain, thalamus and striatum in healthy controls compared with patients receiving SSRI therapy., Conclusion: ¹²³I-mZIENT may be a promising radioligand for imaging the serotonin transporters in humans with acceptable dosimetry.

The study aimed to compare and evaluate the bioequivalence of a new generic preparation of trospium chloride (CAS NO:10405-02-4) capsule (20 mg, test) and the available import tablet (20 mg , reference) for the requirement of state regulatory criteria in China. A randomized- sequence, 2-period crossover study was conducted in 20 healthy Chinese male volunteers in the fasted state. Blood samples were collected before and 1, 2, 3, 4, 5, 6, 7, 8, 12, 24, 36, 48, 60 h after administration of a single oral dose of 40 mg trospium chloride capsules or tablets, followed by a 7-day washout period. The concentration of trospium chloride was determined by a LC-MS/MS method. Drug And Statistical-Version 2.0 was used to calculate the pharmacokinetics parameters and assess bioequivalence of the two preparations. It was considered bioequivalent if the 90% CIs of the mean ratios (test: reference) for Cmax, AUC0-t and AUC0-∞ were within the range from 80% to 125%, respectively. The main pharmacokinetics parameters of test and reference were as follows: t1/2 was (15.11 ± 3.24) h and (16.00 ± 3.96) h; Tmax was (4.0 ± 1.2) h and (4.1 ± 0.9) h; Cmax was (3.76 ± 1.87) ng·mL - 1 and (3.70 ± 1.89) ng·mL - 1; AUC0-t was (33.51 ± 14.39) ng·mL - 1·h and (33.33 ± 14.88) ng·mL - 1·h, and the AUC0-∞ was (35.20 ± 14.88) ng·mL - 1·h and (35.16±15.17) ng·mL - 1·h. The ratios (test: reference) for Cmax, AUC0-t, and AUC0-∞ were 94.0%~111.7%, 96.4%~106.8%, and 96.1%~105.3%, respectively. No significant differences in pharmacokinetic parameters were found between preparations and periods (p>0.05). No obvious adverse events were monitored throughout the study based on clinical parameters and patient reports., (© Georg Thieme Verlag KG Stuttgart · New York.)

Introduction: [(18)F]FE-PE2I is a promising dopamine transporter (DAT) radioligand. In nonhuman primates, we examined the accuracy of simplified quantification methods and the estimates of radiation dose of [(18)F]FE-PE2I., Methods: In the quantification study, binding potential (BP(ND)) values previously reported in three rhesus monkeys using kinetic and graphical analyses of [(18)F]FE-PE2I were used for comparison. BP(ND) using the cerebellum as reference region was obtained with four reference tissue methods applied to the [(18)F]FE-PE2I data that were compared with the kinetic and graphical analyses. In the whole-body study, estimates of adsorbed radiation were obtained in two cynomolgus monkeys., Results: All reference tissue methods provided BP(ND) values within 5% of the values obtained with the kinetic and graphical analyses. The shortest imaging time for stable BP(ND) estimation was 54 min. The average effective dose of [(18)F]FE-PE2I was 0.021 mSv/MBq, similar to 2-deoxy-2-[(18)F]fluoro-d-glucose., Conclusions: The results in nonhuman primates suggest that [(18)F]FE-PE2I is suitable for accurate and stable DAT quantification, and its radiation dose estimates would allow for a maximal administered radioactivity of 476 MBq in human subjects., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Unlabelled: In nuclear medicine brain imaging, it is important to delineate regions of interest (ROIs) so that the outcome is both accurate and reproducible. The purpose of this study was to validate a new time-saving algorithm (DATquan) for accurate and reproducible quantification of the striatal dopamine transporter (DAT) with appropriate radioligands and SPECT and without the need for structural brain scanning., Methods: In a reconstructed DAT SPECT image, DATquan automatically calculated the ratio at steady state of specifically bound radioligand to nondisplaceable radioligand in tissue (BP(ND)) within striatal ROIs that were delineated by use of a semiautomatic template-based alignment approach. DATquan was tested with (123)I-N-(3-iodoprop-2E-enyl)-2-β-carbomethoxy-3β-(4-methylphenyl) SPECT images from 15 patients. In each image, ROIs were first manually delineated, and then corresponding BP(ND) values were derived by an experienced physician. Afterward, 2 independent novice operators used DATquan to analyze the same 15 images. The resulting DATquan-derived BP(ND) data were compared with the data retrieved by manual delineation to assess the accuracy and reproducibility of DATquan. Also, the operational aspects of DATquan were assessed on the basis of measurements of the mean running time of the algorithm as well as on the basis of quantification of the overlap of the DATquan-delineated ROIs obtained by the 2 operators., Results: The mean algorithm running time was 3 min, and the operators' striatal ROIs had a mean overlap of more than 82%. DATquan-derived BP(ND) values obtained by the 2 operators showed high agreement (the mean difference was 0.00 [SD, 0.05] in the striatum, 0.02 [SD, 0.26] in the putamen, and 0.03 [SD, 0.43] in the caudate nucleus). The interoperator variability was 2.2% (SD, 1.3%) in the striatum, 11.7% (SD, 9.9%) in the putamen, and 12.9% (SD, 4.0%) in the caudate nucleus. DATquan-derived BP(ND) values showed high agreement with the values manually derived by the experienced delineator., Conclusion: DATquan is a freely available, accurate, and highly reproducible method for quantification of DAT binding in the brain by SPECT. Once implemented in clinics, DATquan will serve as a useful and time-saving tool.

Degeneration of the dopaminergic nigrostriatal system and of noradrenergic neurons in the locus coeruleus are important pathological features of Parkinson's disease. There is an urgent need to develop therapies that slow down the progression of neurodegeneration in Parkinson's disease. In the present study, we tested whether the highly specific metabotropic glutamate receptor 5 antagonist, 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine, reduces dopaminergic and noradrenergic neuronal loss in monkeys rendered parkinsonian by chronic treatment with low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Weekly intramuscular 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injections (0.2-0.5 mg/kg body weight), in combination with daily administration of 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine or vehicle, were performed until the development of parkinsonian motor symptoms in either of the two experimental groups (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine versus 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle). After 21 weeks of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment, all 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated animals displayed parkinsonian symptoms, whereas none of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated monkeys were significantly affected. These behavioural observations were consistent with in vivo positron emission tomography dopamine transporter imaging data, and with post-mortem stereological counts of midbrain dopaminergic neurons, as well as striatal intensity measurements of dopamine transporter and tyrosine hydroxylase immunoreactivity, which were all significantly higher in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated animals than in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated monkeys. The 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine treatment also had a significant effect on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced loss of norepinephrine neurons in the locus coeruleus and adjoining A5 and A7 noradrenaline cell groups. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated animals, almost 40% loss of tyrosine hydroxylase-positive norepinephrine neurons was found in locus coeruleus/A5/A7 noradrenaline cell groups, whereas the extent of neuronal loss was lower than 15% of control values in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated monkeys. Our data demonstrate that chronic treatment with the metabotropic glutamate receptor 5 antagonist, 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine, significantly reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity towards dopaminergic and noradrenergic cell groups in non-human primates. This suggests that the use of metabotropic glutamate receptor 5 antagonists may be a useful strategy to reduce degeneration of catecholaminergic neurons in Parkinson's disease.

Unlabelled: Current SPECT radioligands available for in vivo imaging of the dopamine transporter (DAT) also show affinity for monoamine transporters other than DAT, especially the serotonin transporter (SERT). The effect of this lack of selectivity for in vivo imaging is unknown. In this study, we compared the SPECT radioligands (123)I-2-β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)nortropane ((123)I-FP-CIT) and (123)I-N-(3-iodoprop-2E-enyl)-2-β-carbomethoxy-3β-(4-methylphenyl) nortropane ((123)I-PE2I), which has a 10-fold higher selectivity than (123)I-FP-CIT for DAT versus SERT [corrected]., Methods: Sixteen healthy individuals were scanned in random order with both radioligands. The radioligands were administered according to standard recommendations: (123)I-FP-CIT was given as a bolus injection, and the ratio between the striatum and reference tissue was measured after 3 h. (123)I-PE2I was administered in a bolus-infusion setup, and the nondisplaceable binding potential (BP(ND)) was measured after 2 h. To assess the contribution of SERT to the overall SPECT signal, SERT was blocked by intravenous citalopram in 6 of the individuals., Results: The striatum-to-reference ratio - 1 of (123)I-FP-CIT was on average 18% higher than the striatal BP(ND) of (123)I-PE2I. Equal doses of radioactivity resulted in 3 times higher counting rates for (123)I-FP-CIT than for (123)I-PE2I, both in target and in reference brain regions. Citalopram infusion led to significant reductions in both striatal (22.8% ± 20.4%, P < 0.05) and thalamic (63.0% ± 47.9%, P < 0.05) (123)I-FP-CIT binding ratios, whereas BP(ND) of (123)I-PE2I was unaltered. Likewise, blocking of SERT led to increased (21% ± 30.1%, P < 0.001) plasma (123)I-FP-CIT, probably as a result of significant blocking of peripheral SERT binding sites. By contrast, plasma (123)I-PE2I remained stable., Conclusion: (123)I-FP-CIT and (123)I-PE2I had approximately the same target-to-background ratios, but per injected megabecquerel, (123)I-FP-CIT gave rise to 3-fold higher cerebral counting rates. We found that (123)I-FP-CIT, but not (123)I-PE2I, brain images have a highly interindividual but significant signal contribution from SERT. Whether the SERT signal contribution is of clinical importance needs to be established in future patient studies.

The N-(E)-fluorobutenyl-3beta-(para-halo-phenyl)nortropanes 9-12 were synthesized as ligands of the dopamine transporter (DAT) for use as (18)F-labeled positron emission tomography (PET) imaging agents. In vitro competition binding assays demonstrated that compounds 9-12 have a high affinity for the DAT and are selective for the DAT compared to the serotonin and norepinephrine transporters. MicroPET imaging with [(18)F]9-[(18)F]11 in anesthetized cynomolgus monkeys showed high uptake in the putamen with lesser uptake in the caudate, but significant washout of the radiotracer was only observed for [(18)F]9. PET imaging with [(18)F]9 in an awake rhesus monkey showed high and nearly equal uptake in both the putamen and caudate with peak uptake achieved after 20 min followed by a leveling-off for about 10 min and then a steady washout and attainment of a quasi-equilibrium. During the time period 40-80 min postinjection of [(18)F]9, the ratio of uptake in the putamen and caudate vs cerebellum uptake was > or = 4.

Background: Muscarinic receptors in the brain play an important role in cognitive function, especially memory, and there is growing awareness that specific antimuscarinic drugs for overactive bladder (OAB) may have adverse central nervous system (CNS) effects. Selection of an antimuscarinic OAB drug with reduced potential for CNS effects could be especially beneficial in the elderly people, in whom even the modest cognitive impairment may negatively affect independence., Purpose: The purpose of the study is to determine if trospium chloride is assay detectable in the CNS of older adults with OAB and to assess whether deterioration of memory occurs in these individuals., Methods: Twelve cognitively intact older adults (>or=65-75 years old) with OAB were given extended-release trospium chloride 60 mg once daily over a 10-day period to achieve plasma steady-state levels. Standardised memory testing (Hopkins Verbal Learning Test-Revised and Brief Visuospatial Memory Test-Revised) was performed predose and postdose. Cerebrospinal spinal fluid (CSF) and plasma samples were drawn on day 10 and assayed for trospium chloride. Predose (day 0) and postdose (day 10) results on the memory tests were compared using a reliable change index to assess a meaningful change in learning or memory., Results: Trospium chloride levels in all the CSF samples (n = 72) of all participants were assay undetectable (<40 pg/ml) on day 10 at steady-state peak plasma concentration concurrent with measureable peak plasma values (C(max) = 925 pg/ml). Repeat memory testing revealed no significant net drug effect on learning or recall., Conclusions: This is the first study to investigate for the presence of an OAB antimuscarinic in the human brain, performed by assaying for concentrations of trospium chloride and correlating with simultaneous clinical cognitive safety measures. The results of both pharmacological and neuropsychological testing support the hypothesis of a lack of detectable CNS penetration for the quaternary amine trospium chloride.

Introduction: Serotonin dysfunction has been linked to a variety of psychiatric diseases; however, an adequate SPECT radioligand to probe the serotonin transporter system has not been successfully developed. The purpose of this study was to characterize and determine the in vivo selectivity of iodine-123-labeled 2beta-carbomethoxy-3beta-(4'-((Z)-2-iodoethenyl)phenyl)nortropane, [(123)I]p ZIENT, in nonhuman primate brain., Methods: Two ovariohysterectomized female baboons participated in nine studies (one bolus and eight bolus to constant infusion at a ratio of 9.0 h) to evaluate [(123)I]p ZIENT. To evaluate the selectivity of [(123)I]p ZIENT, the serotonin transporter blockers fenfluramine (1.5, 2.5 mg/kg) and citalopram (5 mg/kg), the dopamine transporter blocker methylphenidate (0.5 mg/kg) and the norepinephrine transporter blocker nisoxetine (1 mg/kg) were given at 8 h post-radiotracer injection., Results: In the bolus to constant infusion studies, equilibrium was established by 4-8 h. [(123)I]p ZIENT was 93% and 90% protein bound in the two baboons and there was no detection of lipophilic radiolabeled metabolites entering the brain. In the high-density serotonin transporter regions (diencephalon and brainstem), fenfluramine and citalopram resulted in 35-71% and 129-151% displacement, respectively, whereas methylphenidate and nisoxetine did not produce significant changes (<10%)., Conclusion: These findings suggest that [(123)I]p ZIENT is a favorable compound for in vivo SPECT imaging of serotonin transporters with negligible binding to norepinephrine and dopamine transporters., (Copyright 2010 Elsevier Inc. All rights reserved.)

Purpose: This study compares 2beta-carbomethoxy-3beta-(4-[(18)F]fluorophenyl)tropane ([(18)F]beta-CFT) and N-(3-[(18)F]fluoropropyl)-2beta-carbomethoxy-3beta-(4-fluorophenyl)nortropane ([(18)F]beta-CFT-FP) as radiotracers for imaging the dopamine transporter (DAT) in rat., Procedures: Biodistribution, specificity and selectivity of the radiotracers were studied ex vivo in rats pre-treated with specific antagonists for DAT, serotonin transporter (SERT) and noradrenalin transporter (NET) and in control rats. Positron emission tomography (PET) studies were performed using an HRRT scanner. Radiolabelled metabolites were analyzed with thin-layer chromatography., Results: [(18)F]beta-CFT showed slow kinetics with a maximum striatum/cerebellum uptake ratio of 9.2 at 120 min. [(18)F]beta-CFT-FP showed fast kinetics with a maximum ratio of 3.1 at 5 min. Both tracers bound to DAT. [(18)F]beta-CFT also bound to NET. [(18)F]beta-CFT was more resistant to metabolism than [(18)F]beta-CFT-FP., Conclusions: Structural modifications of [(18)F]beta-CFT significantly changed its biological properties, as shown by [(18)F]beta-CFT-FP. [(18)F]beta-CFT is a suitable tracer for both preclinical and human PET studies, but [(18)F]beta-CFT-FP is less suitable as a PET tracer.

A highly sensitive, specific and evaporation free SPE extraction, LC-MS/MS method has been developed for the estimation of trospium in human plasma using trospium-d8 as an internal standard (IS). The analyte was separated using isocratic mobile phase on reverse phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M(+)] cations, m/z 392-164 for trospium and m/z 400-172 for the IS. The total run time was 3.50 min and the elution of trospium and trospium-d8 (IS) occurred at 2.8 min. The developed method was validated in human plasma with a lower limit of quantification of 0.05 ng/mL. A linear response function was established for the range of concentrations 0.05-10 ng/mL (r>0.998) for trospium in human plasma. The intra- and inter-day precision values for trospium met the acceptance as per FDA guidelines. Trospium was stable in the battery of stability studies viz., bench-top, auto-sampler, dry extracts and freeze/thaw cycles. The developed assay method was applied to an oral pharmacokinetic study in humans., (Copyright 2010 Elsevier B.V. All rights reserved.)