Pharmacokinetic and mass balance study of unlabelled and 14 C-labelled emedastine difumarate in healthy volunteers

1. In a mass balance study, six healthy male volunteers received a single oral dose of 4?mg 14 C-labelled emedastine difumarate. The pharmacokinetics of the total radioactivity and unchanged drug were assessed over 48 h. Urinary and faecal excretion were measured over 120 h. Additionally, urinary metabolites were investigated. 2. In a single- and multiple-dose pharmacokinetic study, nine male and nine female healthy volunteers received 2?mg oral emedastine difumarate b.i.d. or 4?mg o.d. for 7 consecutive days. The plasma pharmacokinetics were assessed on day 1 and at steady-state. 3. The mass balance study demonstrated almost complete gastrointestinal absorption of the administered dose. A total of 94.2% of the radioactivity was eliminated via the kidneys. Unchanged emedastine in the urine accounted for <5% of dose. 5-Hydroxy, 6-hydroxy and N -oxide metabolites previously identified in the Japanese were present in Caucasian subjects. 4. AUC after single and multiple dosing were dose-proportional. On day 7, no statistical difference in AUC 0-24 could be detected between the two regimens, with AUC = 70.6 ± 36.1 and 71.7 ± 52.3 ng h ml -1, respectively. There were no gender differences in the pharmacokinetics of emedastine. 5. The results corroborate the use of emedastine in a Caucasian population and support the extrapolation of safety and efficacy data from Asians to Caucasians.     

A validation study comparing accelerator MS and liquid scintillation counting for analysis of 14C-labelled drugs in plasma, urine and faecal extracts

A comparison has been made between accelerator mass spectrometry (AMS) analysis and liquid scintillation counting (LSC) of plasma, urine and faecal samples containing 14C-labelled drugs. In an in vitro study in which human plasma was spiked (the term spiked is used in Section 2.6) with 14C-Fluconazole (14C-FL) over a concentration range of 0.1-2.5 dpm/ml, a correlation coefficient of 0.999 was determined for AMS analysis versus extrapolated LSC data. No significant day to day (or inter-day)variation was seen (P < 0.05 by ANOVA). Coefficients of variation for these analyses ranged from 2.68 to 6.50%. In vivo studies in which rats were given a high (11.5 microCi/kg) or low (18.1 nCi/kg) radioactive dose (to model an exposure of 0.9 microSievert to man) of 14C-Fluticasone propionate(14C-FP) showed that there was also a good correspondence between AMS and LSC data. A mass balance study in a single the faeces by 96 h; less than 1% of the administered dose was excreted in the urine. The limit of reliable measurement of drug related material, above background concentrations, by AMS analysis in this study was approximately 0.1 dpm/ml for plasma, 0.01 dpm/ml for urine without any sample extraction or concentration and 0.01 dpm/ml for faecal extracts. The data reported here demonstrate that AMS is an ultrasensitive and reliable method for analysing 14C-labelled drugs in human and animal body fluids.     

Radiosynthesis of sigma receptor ligands for positron emission tomography: 11C- and 18F-labeled guanidines.

A series of analogues of the potent and selective sigma receptor ligand 1,3-ditolylguanidine (DTG) were synthesized and demonstrated to have high affinity for the sigma receptor as measured by in vitro [3H]DTG displacement studies using guinea pig brain tissue. Three of these 1-aryl-3-(1-adamantyl)guanidines were radiolabeled--two with carbon-11 and one with fluorine-18. Radiochemical yields and specific activities were sufficient for these radiotracers to be used in positron emission tomography imaging of the haloperidol-sensitive sigma receptor.     

Pharmacokinetic and mass balance study of unlabelled and (14)C-labelled emedastine difumarate in healthy volunteers

1. In a mass balance study, six healthy male volunteers received a single oral dose of 4 mg (14)C-labelled emedastine difumarate. The pharmacokinetics of the total radioactivity and unchanged drug were assessed over 48 h. Urinary and faecal excretion were measured over 120 h. Additionally, urinary metabolites were investigated. 2. In a single- and multiple-dose pharmacokinetic study, nine male and nine female healthy volunteers received 2 mg oral emedastine difumarate b.i.d. or 4 mg o.d. for 7 consecutive days. The plasma pharmacokinetics were assessed on day 1 and at steady-state. 3. The mass balance study demonstrated almost complete gastrointestinal absorption of the administered dose. A total of 94.2% of the radioactivity was eliminated via the kidneys. Unchanged emedastine in the urine accounted for <5% of dose. 5-Hydroxy, 6-hydroxy and N-oxide metabolites previously identified in the Japanese were present in Caucasian subjects. 4. AUC after single and multiple dosing were dose-proportional. On day 7, no statistical difference in AUC(0-24) could be detected between the two regimens, with AUC = 70.6 +/- 36.1 and 71.7 +/- 52.3 ng h ml(-1), respectively. There were no gender differences in the pharmacokinetics of emedastine. 5. The results corroborate the use of emedastine in a Caucasian population and support the extrapolation of safety and efficacy data from Asians to Caucasians.     

A human capecitabine excretion balance and pharmacokinetic study after administration of a single oral dose of 14C-labelled drug

An excretion balance and pharmacokinetic study was conducted in cancer patients with solid tumors who received a single oral dose of capecitabine of 2000 mg including 50 Ci of ¹⁴C-radiolabelled capecitabine. Blood, urine and fecal samples were collected until radioactive counts had fallen to below 50 dpm/mL in urine, and levels of intact drug and its metabolites were measured in plasma and urine by LC/MS-MS (mass spectrometry) and ¹⁹F-NMR (nuclear magnetic resonance) respectively. Based on the results of the 6 eligible patients enrolled, the dose was almost completely recovered in the urine (mean 95.5%, range 86–104% based on radioactivity measurements) over a period of 7 days after drug administration. Of this, 84% (range 71–95) was recovered in the first 12 hours. Over this time period, 2.64% (0.69–7.0) was collected in the feces. Over a collection period of 24–48h, a total of 84.2% (range 80–95) was recovered in the urine as the sum of the parent drug and measured metabolites (5-DFCR, 5-DFUR, 5-FU, FUH₂, FUPA, FBAL). Based on the radioactivity measurements of drug-related material, absorption is rapid (t_max 0.25–1.5 hours) followed by a rapid biphasic decline. The parent drug is rapidly converted to 5-FU, which is present in low levels due to the rapid metabolism to FBAL, which has the longest half-life. There is a good correlation between the levels of radioactivity in the plasma and the levels of intact drug and the metabolites, suggesting that these represent the most abundant metabolites of capecitabine. The absorption of capecitabine is rapid and almost complete. The excretion of the intact drug and its metabolites is rapid and almost exclusively in the urine.     

The application of accelerator mass spectrometry to absolute bioavailability studies in humans: simultaneous administration of an intravenous microdose of 14C-nelfinavir mesylate solution and oral nelfinavir to healthy volunteers

The absolute bioavailability of nelfinavir was determined in 6 healthy volunteers following simultaneous administration of 1250 mg oral nelfinavir and an intravenous infusion of (14)C-nelfinavir mesylate on day 1 and at steady state. Nelfinavir oral bioavailability decreased from 0.88 to 0.47 over the 11-day study period. The moderate bioavailability of nelfinavir was due to significant first-pass metabolism rather than low absorption, limiting the potential of formulation improvement to decrease pill burden. Human absolute bioavailability studies with accelerator mass spectrometry microdosing, in which an intravenous microdose is given along with a conventional oral dose of the same drug, can differentiate between gastrointestinal absorption and the first-pass metabolism of new drug candidates. Accelerator mass spectrometry allowed a several thousand-fold dose reduction of (14)C-nelfinavir relative to that required for liquid scintillation counting. Accelerator mass spectrometry microdosing reduces potential safety issues around dosing radioactivity to humans and prevents the need to formulate high intravenous doses.     

Age, sex and NK1 receptors in the human brain -- a positron emission tomography study with [(11)C]GR205171

The substance P/neurokinin 1 (SP/NK1) system has been implicated in the processing of negative affect. Its role seems complex and findings from animal studies have not been easily translated to humans. Brain imaging studies on NK1 receptor distribution in humans have revealed an abundance of receptors in cortical, striatal and subcortical areas, including the amygdala. A reduction in NK1 receptors with increasing age has been reported in frontal, temporal, and parietal cortices, as well as in hippocampal areas. Also, a previous study suggests sex differences in cortical and subcortical areas, with women displaying fewer NK1 receptors. The present PET study explored NK1 receptor availability in men (n=9) and women (n=9) matched for age varying between 20 and 50years using the highly specific NK1 receptor antagonist [(11)C]GR205171 and a reference tissue model with cerebellum as the reference region. Age by sex interactions in the amygdala and the temporal cortex reflected a lower NK1 receptor availability with increasing age in men, but not in women. A general age-related decline in NK1 receptor availability was evident in the frontal, temporal, and occipital cortices, as well as in the brainstem, caudate nucleus, and thalamus. Women had lower NK1 receptor availability in the thalamus. The observed pattern of NK1 receptor distribution in the brain might have functional significance for brain-related disorders showing age- and sex-related differences in prevalence.     

Effects of fluoxetine on dopamine D2 receptors in the human brain: a positron emission tomography study with [11C]raclopride

We have previously reported that repeated dosing with the selective serotonin reuptake inhibitor (SSRI) citalopram decreases striatal [11C]raclopride binding in healthy volunteers. As the SSRI-class antidepressant drugs are believed to have a similar mechanism of action, we wanted to explore whether the prototype SSRI drug, fluoxetine, shares the effects of citalopram on subcortical dopamine neurotransmission. Eight healthy male volunteers were studied using a randomized double-blind placebo-controlled study design. Striatal and thalamic D2-receptor binding was measured at baseline, after a single oral dose (20 mg) of fluoxetine, and after repeated dosing (2 wk, 20 mg/d). The D2-receptor binding potential (BP) was assessed using [11C]raclopride and 3D positron emission tomography. Repeated dosing of fluoxetine decreased BP in the right medial thalamus (p=0.022). Fluoxetine did not decrease striatal BP, but there was a trend (p=0.090) towards increased BP in the left putamen after repeated dosing. A single dose of fluoxetine did not affect BP in the thalamus or striatum. Fluoxetine appears to have a regionally selective effect on the dopaminergic neurotransmission in various areas of the brain. The current results after fluoxetine together with our previous data on citalopram suggest that the modulatory effects of these drugs on striatal dopaminergic neurotransmission are different upon repeated dosing and further substantiates pharmacological differences between SSRI-class drugs.     

A phase I,open-label,single-dose micro tracer mass balance study of 14C-labeled ASP7991 in healthy Japanese male subjects using accelerator mass spectrometry

ASP7991 is a calcimimetic that acts on the calcium-sensing receptor on parathyroid cell membranes and suppresses parathyroid hormone (PTH) secretion in the treatment of secondary hyperparathyroidism. The mass balance and metabolite profile of [¹⁴C]ASP7991 were investigated in six healthy male subjects after a single oral dose of [¹⁴C]ASP7991 [1 mg, 18.5 kBq (500 nCi)] in solution. [¹⁴C] radioactivity in plasma, urine and feces was analyzed using Accelerator mass spectrometry. ASP7991 was rapidly absorbed, metabolized and excreted. Mean recovery of [¹⁴C] radioactivity in urine and feces was 30.08% and 49.31%, respectively, and mean total recovery of [¹⁴C] radioactivity was 79.39%. The majority of [¹⁴C] radioactivity in urine and feces was excreted within the first 72 h following administration. Seven metabolites were detected in plasma, urine and feces samples, and their structures were determined by mass spectrometry. The main metabolic pathways of ASP7991 in humans were predicted to be N-dealkylation, followed by N-acetylation and taurine conjugation to a carboxylic acid moiety. Our findings show that a mass balance study using micro radioactivity doses is suitable for elucidating the pharmacokinetics of the absorption, metabolism and excretion of administered drugs.     

Serotonin 1A receptor availability in patients with schizophrenia and schizo-affective disorder: a positron emission tomography imaging study with [11C]WAY 100635

Background Postmortem and positron emission tomography (PET) studies have reported several alterations in serotonin 1A receptor (5-HT_1A) binding parameters in patients with schizophrenia. This study examines 5-HT_1A availability in vivo in individuals with schizophrenia and schizo-affective disorder.Materials and methods Twenty-two medication-free individuals with schizophrenia or schizo-affective disorder and 18 healthy subjects underwent PET scans with [¹¹C]WAY 100635. Regional distribution volumes (V _T, in milliliters per gram) were derived using a two-tissue compartment kinetic model. Outcome measures for 5-HT_1A availability included binding potential (BP) and the specific to nonspecific equilibrium partition coefficient (V ₃″). Eleven brain regions with high density of 5-HT_1A were included in the analysis.Results No significant differences were observed in regional BP or V ₃″ between patients and controls. No significant relationships were observed between regional 5-HT_1A availability and symptom severity.Conclusion The postmortem literature reports increased 5-HT_1A binding in the prefrontal cortex in schizophrenia. This study did not detect differences in 5-HT_1A binding. Whereas in two recently published PET studies, one reports increased binding in the temporal lobe while the other reports decreased binding in the amygdala. These inconsistencies suggest that the alterations demonstrated in postmortem studies cannot be reliably detected at the resolution achieved with PET. This raises the question as to whether major changes in the level of expression of the 5-HT_1A receptor play a role in the pathophysiology of schizophrenia.Dr. Lombardo participated in this work while at Columbia University but subsequently has moved to Pfizer Inc., 235 east 42nd Street MS 10/33, New York, NY 10017, USA.     

维拉帕米联合氯沙坦钾治疗高血压的临床研究

目的探讨维拉帕米联合氯沙坦钾治疗高血压的临床疗效。方法选取2018年2月—2019年2月在首都医科大学附属北京天坛医院治疗的高血压患者96例,根据用药的差别分为对照组(48例)和治疗组(48例)。对照组口服氯沙坦钾片,起始剂量50 mg/次,1次/d,必要时可增至100 mg/次,1次/d;治疗组在对照组的基础上口服盐酸维拉帕米片,起始剂量80 mg/次,3次/d,最大剂量360～480 mg/d,对于低剂量即有反应的老年人或体型瘦小者,起始40 mg/次,3次/d。两组患者治疗4周。观察两组患者临床疗效,同时比较治疗前后两组患者血压、C反应蛋白(CRP)、可溶性凝集素样氧化低密度脂蛋白受体1(s LOX-1)、可溶性细胞间粘附分子-1(s ICAM-1)、基质金属蛋白酶-9(MMP-9)、转化生长因子β1(TGF-β1)、单核细胞趋化蛋白1(MCP-1)和血管内皮功能。结果治疗后,对照组临床有效率为81.25%,显著低于治疗组的97.92%,两组比较差异有统计学意义(P0.05)。治疗后,两组患者收缩压(SBP)、舒张压(DBP)均显著下降(P0.05),且治疗组患者血压水平明显低于对照组(P0.05)。治疗后,两组患者血清CRP、s LOX-1、s ICAM-1、MMP-9、TGF-β1、MCP-1水平均明显降低(P0.05),且治疗组患者这些血清细胞因子水平明显低于对照组患者(P0.05)。治疗后,两组肱动脉内皮依赖性舒张功能(EDD)、肱动脉非内皮依赖的舒张功能(NMD)均明显升高(P0.05),且治疗组患者血管内皮功能明显高于对照组(P0.05)。结论维拉帕米联合氯沙坦钾治疗高血压可显著降低患者血压,改善患者临床症状和血管内皮功能。     

心脉通胶囊联合维拉帕米治疗高血压的临床研究

目的探索心脉通胶囊联合维拉帕米治疗高血压的临床效果。方法选取了2017年9月—2020年9月平顶山市第二人民医院收治的128例高血压患者为研究对象,按照随机数字表法分为对照组和治疗组,每组各64例。对照组口服盐酸维拉帕米缓释片,1片/次,2次/d;治疗组在对照组基础上口服心脉通胶囊,3粒/次,3次/d。两组均连续服用4周。观察两组的临床疗效,比较两组治疗前后血压和血清细胞因子的变化情况及不良反应发生情况。结果治疗后,治疗组总有效率89.06%,显著高于对照组76.66%(P0.05)。治疗后,两组舒张压、收缩压均较治疗前显著降低(P0.05);且治疗后治疗组舒张压、收缩压显著低于对照组(P0.05)。治疗后,治疗组血清C反应蛋白(CRP)、基质金属蛋白酶9(MMP-9)、转化生长因子β1(TGF-β1)、单核细胞趋化因子(MCP)水平均显著降低(P0.05);且治疗后,治疗组血清细胞因子水平显著低于对照组(P0.05)。治疗过程中,治疗组患者不良反应发生率是3.13%,显著低于对照组的18.75%(P0.05)。结论心脉通胶囊联合维拉帕米治疗高血压患者具有较好的临床疗效,可降低血压指标和炎性因子水平,适合临床推广应用。     

Determination of the bioavailability of [14C]-hexaminolevulinate using accelerator mass spectrometry after intravesical administration to human volunteers

Hexaminolevulinate (HAL) is a diagnostic agent that allows the visualization of tumor tissue in the bladder by fluorescence cystoscopy. It is administered intravesically via a catheter for 1 hour, followed by blue light bladder inspection to induce selective red tumor fluorescence. Hexaminolevulinate should ideally be confined to the bladder only, but it is likely that some absorption occurs during administration, and therefore the systemic bioavailability is of interest. The bioavailability of HAL was determined by intravesical and intravenous administration of [14C]-HAL hydrochloride to 8 human volunteers. To reduce the radiation dose as low as possible, the ultrasensitive analytical technique of accelerator mass spectrometry was used to measure [14C]-HAL. The bioavailability of [14C]-HAL after intravesical and intravenous administration was determined from the respective area under the curve based on total radioactivity and was determined to be 7% (range, 5%-10%; 90% confidence interval). The systemic absorption of [14C]-HAL after intravesical administration is low and supports previous clinical experience with HAL showing no systemic side effects.     

Imaging human reward processing with positron emission tomography and functional magnetic resonance imaging

Functional neuroimaging (fMRI) studies show activation in mesolimbic circuitry in tasks involving reward processing, like the Monetary Incentive Delay Task (MIDT). In voltammetry studies in animals, mesolimbic dopamine release is associated with reward salience. This study examined the relationship between fMRI activation and magnitude of dopamine release measured with Positron emission tomography study (PET) in the same subjects using MIDT in both modalities to test if fMRI activation is related to dopamine release. Eighteen healthy subjects were scanned with [¹¹ C]raclopride PET at baseline and after MIDT. Binding potential (BP_ND) was derived by equilibrium analysis in striatal subregions and percent change across conditions (∆BP_ND) was measured. Blood oxygen level dependence (BOLD) signal changes with MIDT were measured during fMRI using voxelwise analysis and ROI analysis and correlated with ∆BP_ND. ∆BP_ND was not significant in the ventral striatum (VST) but reached significance in the posterior caudate. The fMRI BOLD activation was highest in VST. No significant associations between ∆BP_ND and change in fMRI BOLD were observed with VST using ROI analysis. Voxelwise analysis showed positive correlation between BOLD activation in anticipation of the highest reward and ∆BP_ND in VST and precommissural putamen. Our study indicates that endogenous dopamine release in VST is of small magnitude and is related to BOLD signal change during performance of the MIDT in only a few voxels when rewarding and nonrewarding conditions are interspersed. The lack of correlation at the ROI level may be due to the small magnitude of release or to the particular dependence of BOLD on glutamatergic signaling.     

Modelling human drug abuse and addiction with dedicated small animal positron emission tomography

Drug addiction is a chronically relapsing brain disorder, which causes substantial harm to the addicted individual and society as a whole. Despite considerable research we still do not understand why some people appear particularly disposed to drug abuse and addiction, nor do we understand how frequently co-morbid brain disorders such as depression and attention-deficit hyperactivity disorder (ADHD) contribute causally to the emergence of addiction-like behaviour. In recent years positron emission tomography (PET) has come of age as a translational neuroimaging technique in the study of drug addiction, ADHD and other psychopathological states in humans. PET provides unparalleled quantitative assessment of the spatial distribution of radiolabelled molecules in the brain and because it is non-invasive permits longitudinal assessment of physiological parameters such as binding potential in the same subject over extended periods of time. However, whilst there are a burgeoning number of human PET experiments in ADHD and drug addiction there is presently a paucity of PET imaging studies in animals despite enormous advances in our understanding of the neurobiology of these disorders based on sophisticated animal models. This article highlights recent examples of successful cross-species convergence of findings from PET studies in the context of drug addiction and ADHD and identifies how small animal PET can more effectively be used to model complex psychiatric disorders involving at their core impaired behavioural self-control.     

Diminished brain 5-HT transporter binding in major depression: a positron emission tomography study with [11C]DASB

Background

The serotonin transporter (5-HTT) plays a critical role in the regulation of serotonin neurotransmission and has been implicated in the pathophysiology of major depression. In a previous positron emission tomography study, we found no difference in brain 5-HTT binding between unmedicated recovered depressed patients and healthy controls.

Aim

This study aims to assess brain 5-HTT binding in a group of unmedicated acutely depressed patients in comparison to healthy controls.

Methods

We studied 5-HTT binding using [¹¹C]DASB in conjunction with positron emission tomography in 12 medication-free depressed patients with a mean duration of illness of about 1?year and 24 healthy controls.

Results

The depressed patients had lowered 5-HTT binding in several brain regions including brain stem, thalamus, caudate, putamen, anterior cingulate cortex and frontal cortex.

Conclusions

These results suggest that diminished availability of the 5-HTT in the brain may be a state marker of acute depression. Alternatively, low 5-HTT binding may delineate a group of depressed patients with a poor long-term prognosis.     

A microdose study of 14C-AR-709 in healthy men: pharmacokinetics, absolute bioavailability and concentrations in key compartments of the lung

Purpose

To explore, in a microdose (phase-0) study, the pharmacokinetics, bioavailability and concentrations in key compartments of the lung, of AR-709, a novel diaminopyrimidine antibiotic for the treatment of respiratory infection.

Methods

Four healthy men each received two single, 100 μg microdoses of ¹⁴C-AR-709, 7 days apart: the first was administered intravenously (IV), the second orally. Plasma pharmacokinetics of ¹⁴C and unchanged AR-709 were obtained by high-performance liquid chromatography and accelerator mass spectrometry (AMS). Next, 15 healthy men received a single, 100 μg microdose of ¹⁴C-AR-709 IV. Plasma, bronchoalveolar lavage fluid, alveolar macrophages and bronchial mucosal biopsy samples were analysed by AMS.

Results

After IV administration, clearance of AR-709 was 496 mL/min, volume of distribution was 1,700 L and the absolute oral bioavailability was 2.5 %. Excretion in urine was negligible. At 8–12 h after IV dosing, ¹⁴C concentrations in lung samples were 15- (bronchial mucosa) to 200- (alveolar macrophages) fold higher than in plasma. In alveolar macrophages, ¹⁴C was still mostly associated with AR-709 at 12 h after dosing.

Conclusions

The results of this microdose study indicate that AR-709 attains concentrations appreciably higher within the lung than in plasma. Its low oral bioavailability however, precludes oral administration. Although IV administration would appear to be an effective route of administration, this would limit the use of AR-709 to a clinical setting and would therefore be economically unsustainable. If further clinical development were to be undertaken, therefore, an alternative route of administration would be necessary.