Physiological Animal Imaging with 68Ga-Citrate.

BACKGROUND: Gallium-68 is an ideal research and hospital-based PET radioisotope. The uptake mechanism of Gallium citrate is a combination of specific and non-specific processes, for example, vasodilatation, increased vascular permeability, plasma transferrin binding and lactoferrin and siderophores. OBJECTIVE: In this study, by applying the 68Ge/68Ga generator product, a simple technique for the synthesis and quality control of 68Ga-citrate was introduced and was followed by preliminary animal studies. METHODS: The synthesis of 68Ga-citrate was performed with a cationic method using the Scintomics automated synthesis system (Scintomics GmbH GRP module 4V). Since the standard procedure for quality control (QC) was not available, the definition of chemical and radiochemical purity of 68Ga-citrate was carried out according to the ICH Q2(R1) guideline. The standard QC tests were analysed with Scintomics 8100 radio-HPLC system equipped with a radioactivity detector. In this study, a New Zealand rabbit weighing 2520 g was used for PET/CT images. RESULTS: 68Ga-citrate synthesis was performed by a cationic method without using organic solvents. The labelling efficiency was found to be >98%. The HPLC method used to assess the radiochemical purity of 68Ga -citrate was validated as rapid, accurate and reproducible enough to apply it to patients safely. The physiological distribution of 68Ga-citrate was investigated in a healthy rabbit. The blood pool, liver, spleen, kidneys and growth plates were the most common sites of 68Ga-citrate involvement.

Effects of Caffeine on Splanchnic Oxygenation in Preterm Infants.

OBJECTIVE: The aim of this study is to assess the effects of administering 20 mg/kg loading dose of caffeine citrate intravenously on splanchnic oxygenation in preterm infants. STUDY DESIGN: The infants with a gestational age (GA) of <34 weeks who were administered with a 20 mg/kg intravenous loading dose of caffeine citrate within 48 hours after birth were investigated prospectively. Regional splanchnic oxygen saturation (rsSO2) and splanchnic fractional tissue oxygen extraction rate (sFTOE) were measured using near-infrared spectroscopy before caffeine infusion, immediately after caffeine infusion and 1, 2, 3, 4, and 6 hours (h) after dose completion; postdose values were compared with predose values. RESULTS: A total of 41 infants with a mean GA of 29.2 ± 1.6 weeks and birth weight of 1,315 ± 257 g as well as postnatal age of 32.2 ± 10.8 hours were included in the study. rsSO2 significantly reduced from 63.1 to 57.5% immediately after caffeine infusion, 55.1% after 1 hour, and 55.2% after 2 hours with partial recovery at 3-hour postdose. sFTOE increased correspondingly. CONCLUSION: Caffeine reduces splanchnic oxygenation and increases splanchnic oxygen extraction for at least 2 hours with partial recovery to predose levels at 3-hour postdose.

Pharmacokinetics, pharmacodynamics and metabolism of caffeine in newborns.

The plasma elimination half-life of caffeine in the newborn is approximately 100 h. Caffeine is rapidly absorbed with complete bioavailability following oral dosing. Switching between parenteral and oral administration requires no dose adjustments. Caffeine has wide interindividual pharmacodynamic variability and a wide therapeutic index in preterm newborns. Thresholds of measurable efficacy on respiratory drive have been documented at plasma levels around 2 mg/L. At these low levels, caffeine competitively inhibits adenosine receptors (A1 and A2A). The toxicity threshold is ill-defined and possibly as high as 60 mg/L which can be lethal in adults. High doses of caffeine may produce better control of apnea. However, at high systemic drug concentrations, the pharmacodynamic actions of caffeine become more complex and worrisome. They include inhibition of GABA receptors and cholinergic receptors in addition to adenosine receptor inhibition, intracellular calcium mobilization and actions on adrenergic, dopaminergic and phosphodiesterase systems. The role of pharmacogenomic factors as determinants of neonatal pharmacologic response and clinical effects remains to be explored.

Population pharmacokinetic study of caffeine citrate in Chinese premature infants with apnea.

WHAT IS KNOWN AND OBJECTIVES: Caffeine citrate is a commonly used methylxanthine for pharmacologic treatment of apnea of prematurity. The aim of this study was to develop and verify a population pharmacokinetic (PPK) model, which can provide a reference for individualized caffeine citrate treatment of apnea in Chinese premature infants. METHODS: A total of 88 serum concentration measurements from 46 preterm patients (median gestational age 29 weeks) were retrospectively collected and the relevant clinical data of patients were recorded. The PPK analysis was performed by non-linear mixed-effect modelling method using NONMEM. Allometric scaling was applied in the PPK analysis, and the final model was evaluated by graphic and statistical methods, including goodness-of-fit plots, normalized prediction distribution errors plots and bootstrap procedures. RESULTS: A one-compartment model with first-order elimination was successfully fitted to the data. The typical scaled values for the parameters clearance and volume of distribution (V) were 0.268 L/h and 109 L per 70 kg, respectively. The weight at the time of blood collection (CW) and post-natal age were identified as important predictors for pharmacokinetic parameters of caffeine. The evaluation process showed good stability and predictability of the final PPK model. WHAT IS NEW AND CONCLUSION: This is a complete PPK study of caffeine citrate in Chinese premature infants with apnea, which complements caffeine pharmacokinetic data of the premature from China. A final PPK model was developed which may serve as a beneficial tool for the use of caffeine citrate in the treatment of apnea in Chinese preterm infants.

Rapid and cost-effective LC-MS/MS method for determination of hydroxycitric acid in plasma: Application in the determination of pharmacokinetics in commercial Garcinia preparations.

Garcinia cambogia is one of the most commonly used anti-obesity dietary supplements, and hydroxycitric acid (HCA) is a major constituent in the commercial preparations of Garcinia. High doses of HCA are often consumed without much awareness of its pharmacokinetic and toxicokinetic parameters, and therefore, a complete understanding of its effects is lacking. The first step in understanding these parameters is the availability of a reliable bioanalytical method. Here, we present the first report on a UPLC-MS/MS method for analysis of HCA in rat plasma after a simplified and cost-effective protein precipitation. Chromatographic separation of the analytes in the supernatant was achieved using hydrophilic interaction liquid chromatography, where mass parameters were optimized and a rapid 5-min quantitative assay was developed. The method was highly sensitive, accurate, precise and linear in the concentration range of 10.5-5000 ng/mL (validated according to the United States Food and Drug Administration guidelines). Further, the method was successfully used to describe the pharmacokinetic profile of HCA in rat plasma after the administration of pure HCA and commercial Garcinia preparations.

Caffeine preserves quiet sleep in preterm neonates.

Caffeine is widely used in preterm neonates suffering from apnea of prematurity (AOP), and it has become one of the most frequently prescribed medications in neonatal intensive care units. Goal of this study is to investigate how caffeine citrate treatment affects sleep-wake behavior in preterm neonates. The observational study consists of 64 preterm neonates during their first 5 days of life with gestational age (GA) <32 weeks or very low birthweight of < 1500 g. A total of 52 patients treated with caffeine citrate and 12 patients without caffeine citrate were included. Sleep-wake behavior was scored in three stages: active sleep, quiet sleep, and wakefulness. Individual caffeine concentration of every neonate was simulated with a pharmacokinetic model. In neonates with GA ≥ 28 weeks, wakefulness increased and active sleep decreased with increasing caffeine concentrations, whereas quiet sleep remained unchanged. In neonates with GA < 28 weeks, no clear caffeine effects on sleep-wake behavior could be demonstrated. Caffeine increases fraction of wakefulness, alertness, and most probably also arousability at cost of active but not quiet sleep in preterm neonates. As such, caffeine should therefore not affect time for physical and cerebral regeneration during sleep in preterm neonates.

Effects of chronic immobilization stress on biokinetics and dosimetry of 67Ga in a murine model.

The aim of this work is to determine the effect of chronic immobilization stress on kinetics and dosimetry of 67Ga in a mouse model. A control group (CG) and a stress group (SG), each with 15 mice, were included in the study, and the latter group was subjected to a chronic immobilization stress model 2 h daily for 14 consecutive days. At day 13, 67Ga-citrate was administered intraperitoneally (11.24 ± 0.44 MBq) to each mouse. Then, sets of three mice were obtained sequentially at 24, 36, 48, 60 and 72 h, in which the radionuclide activity was measured with an activity counter. The 67Ga biokinetic data showed a fast blood clearance in the SG, with a mean residence time of 0.06 h. The calculated mean radiation absorbed doses were: liver (2.45 × 10-03 Gy), heart (3.17 × 10-04 Gy) and kidney (1.88 × 10-04 Gy) in the SG. The results show that stress reduced weight gain by approximately 13% and also increased adrenal gland weight by 26%. On the other hand, chronic stress accelerates 67Ga clearance after 24 h compared to normal conditions. It is concluded that murine organisms under chronic immobilization stress have higher gallium-67 clearance rates, decreasing the cumulated activity and absorbed dose in all organs.

Measurement, model prediction and uncertainty quantification of plasma clearance of cerium citrate in humans.

Double tracer studies in healthy human volunteers with stable isotopes of cerium citrate were performed with the aim of investigating the gastro-intestinal absorption of cerium (Ce), its plasma clearance and urinary excretion. In the present work, results of the clearance of Ce in blood plasma are shown after simultaneous intravenous and oral administration of a Ce tracer. Inductively coupled plasma mass spectrometry was used to determine the tracer concentrations in plasma. The results show that about 80% of the injected Ce citrate cleared from the plasma within the 5 mins post-administration. The data obtained are compared to a revised biokinetic model of Ce, which was initially developed by the International Commission on Radiological Protection (ICRP). The measured plasma clearance of Ce citrate was mostly consistent with that predicted by the ICRP biokinetic model. Furthermore, in an effort to quantify the uncertainty of the model prediction, the laboratory animal data on which the ICRP biokinetic Ce model is based, was analyzed. The measured plasma clearance and its uncertainty was also compared to the plasma clearance uncertainty predicted by the model. It was found that the measured plasma clearance during the first 15 min after administration is in a good agreement with the modelled plasma clearance. In general, the measured clearance falls inside the 95% confidence interval predicted by the biokinetic model.

A quick and simple in vitro assay to predict bioavailability of actinides following accidental exposure.

Physicochemical properties of actinides highly influence internal intake and biodistribution. An a priori knowledge of the dissolution properties of compounds involved in accidental exposure would be of great help in early dose assessment. However, this information is rarely available, leading to difficulties in interpreting excretion data from contaminated victims. We developed an in vitro acellular assay to predict in vivo bioavailability of actinides and improve medical handling of the victims. Various actinides of different physicochemical properties were used to validate the reliability of the assay to mimic in vivo behavior of the contaminants. Our assay was designed as a dynamic muticompartmental system in which an agarose gel represents the retention compartment of actinides and a dynamic phase the transfer compartment. Relevant physiological conditions were obtained by introducing various components both in the static and dynamic phases. The proposed model may provide a good prediction of in vivo behavior and could be used as a first assessment to predict the fraction of actinides that could be potentially transferred from retention compartments, as well as the fraction available to chelating drugs.

Pharmacokinetic and tissue distributions study of adenosine, 4-hydroxybenzyl alcohol and Parishin C from Gastrodia elata extract in rats.

The plant Gastrodia elata is a type of the orchid plant Gastrodia elata Bl. which contains glycosides, phenols, polysaccharides, sterols, and organic acids and a variety of active ingredients are proved to have certain pharmacological activities. To understand the process in the body of Gastridua elata, we used HPLC to study pharmacokinetics and tissue distributions of adenosine, 4-hydroxybenzyl alcohol and Parishin C in rats. The results showed that the three ingredients could be detected in plasma and different organizations at various time points. There was no significant difference in systemic clearance at three ingredients and it may be show that the three ingredients distributed (0.475±0.025, 0.518±0.033, 0.699±0.051) quickly and eliminated (5.37±0.87, 4.54±0.69, 5.34±0.82) slowly in plasma. There was the highest content of adenosine in spleen, followed by liver and lung. The highest content of 4-hydroxybenzylacohol in liver, and was higher in spleen. Parishin C was highest in heart, followed by liver and spleen. It is obvious that the contents of three ingredients are all higher in liver. The trends of the three ingredients' contents in G. rhizome extract were consistent with the contents in the plasma after intravenous administration.

Technical Pitfall in 68Ga-Prostate Specific Membrane Antigen Imaging: Altered Biodistribution Caused by Free 68Ga-Citrate Due to Radiolysis Showing Increased Vascular Activity.

As with any new molecular imaging modality, accurate characterization of abnormalities on Ga-PSMA PET/CT imaging can be accomplished only if one is aware of the normal distribution pattern, physiological variants, and potential sources of false imaging findings. Altered biodistribution can have a significant impact on scan interpretation. Presented here is a rare case in which radiopharmaceutical radiolysis occurred causing excessive free Ga-citrate showing as an increased vascular activity. As Ga-PSMA PET/CT imaging is a relatively new imaging technique, it is important to be aware of such a potential technical pitfall in clinical practice in order to prevent scan misinterpretation.

Enhanced brain delivery with lower hepatic exposure of lazaroid loaded nanostructured lipid carriers developed using a design of experiment approach.

The current study was designed to develop and optimize lazaroid loaded nano-structured lipid carriers (LAZ-NLCs) using design of experiment approach for enhancing lazaroid brain exposure. Response surface plots were used to determine the effects of independent variables (amount of PEGylating agent and liquid lipid) on dependent variables (particle size, zeta potential and encapsulation efficiency), while numerical optimization was used for optimizing LAZ-NLCs composition. The optimal LAZ-NLCs were spherical in shape with measured size of 172.3 ±â€¯3.54 nm, surface charge of -4.54 ±â€¯0.87 mV and encapsulation efficiency of 85.01 ±â€¯2.60%. The optimal LAZ-NLCs were also evaluated for hemolytic potential, storage stability and solid-state properties. The plasma pharmacokinetics along with brain and hepatic distributions of control lazaroid citrate solution and optimal LAZ-NLCs formulation were evaluated in Sprague-Dawley rats after the single bolus intravenous administration. The optimized LAZ-NLCs and the control lazaroid citrate solution had similar plasma pharmacokinetic profiles; however, differential organ bio-distributions were observed. The lazaroid exposure in brain was enhanced by two times with a decreased liver exposure by half for the NLCs group compared to the solution group.

Caffeine Citrate Dosing Adjustments to Assure Stable Caffeine Concentrations in Preterm Neonates.

OBJECTIVE: To identify dosing strategies that will assure stable caffeine concentrations in preterm neonates despite changing caffeine clearance during the first 8 weeks of life. METHODS: A 3-step simulation approach was used to compute caffeine doses that would achieve stable caffeine concentrations in the first 8 weeks after birth: (1) a mathematical weight change model was developed based on published weight distribution data; (2) a pharmacokinetic model was developed based on published models that accounts for individual body weight, postnatal, and gestational age on caffeine clearance and volume of distribution; and (3) caffeine concentrations were simulated for different dosing regimens. RESULTS: A standard dosing regimen of caffeine citrate (using a 20 mg/kg loading dose and 5 mg/kg/day maintenance dose) is associated with a maximal trough caffeine concentration of 15 mg/L after 1 week of treatment. However, trough concentrations subsequently exhibit a clinically relevant decrease because of increasing clearance. Model-based simulations indicate that an adjusted maintenance dose of 6 mg/kg/day in the second week, 7 mg/kg/day in the third to fourth week and 8 mg/kg/day in the fifth to eighth week assures stable caffeine concentrations with a target trough concentration of 15 mg/L. CONCLUSIONS: To assure stable caffeine concentrations during the first 8 weeks of life, the caffeine citrate maintenance dose needs to be increased by 1 mg/kg every 1-2 weeks. These simple adjustments are expected to maintain exposure to stable caffeine concentrations throughout this important developmental period and might enhance both the short- and long-term beneficial effects of caffeine treatment.

Therapeutic drug monitoring of caffeine in preterm infants: Could saliva be an alternative to serum?

OBJECTIVE: Evaluate whether saliva could be a useful alternative to serum for routine therapeutic drug monitoring of caffeine in preterm infants using the enzyme multiplied immunoassay technique (EMIT) assay. METHODS: We conducted a prospective study including preterm infants (less than 34 weeks' amenorrhea) admitted to the intensive care and neonatal medicine department. All infants received 5, 10, 15, 20 and 25mg/kg/day of citrate caffeine intravenously from the first to the fifth day of birth, respectively. For each patient, two concomitant blood and saliva samples corresponding to the trough concentrations were collected 24hours after each caffeine dose. The caffeine concentrations were determined using the EMIT®2000 caffeine assay. RESULTS: Thirteen preterm infants were included. The saliva and the serum caffeine concentration increased proportionally to the administered dose. Saliva and serum kinetics were comparable and the saliva caffeine concentrations were correlated to the serum ones (r2=0.76). CONCLUSION: Saliva caffeine monitoring by EMIT is a valid, useful and safe alternative to serum in preterm infants.

Exploring cellular uptake of iron oxide nanoparticles associated with rhodium citrate in breast cancer cells.

Nanocarriers have the potential to improve the therapeutic index of currently available drugs by improving their efficacy and achieving therapeutic steady-state levels over an extended period. The association of maghemite-rhodium citrate (MRC) nanoparticles (NPs) has the potential to increase specificity of the cytotoxic action. However, the interaction of these NPs with cells, their uptake mechanism, and subcellular localization need to be elucidated. This work evaluates the uptake mechanism of MRC NPs in metastatic and nonmetastatic breast cancer-cell models, comparing them to a nontumor cell line. MRC NPs uptake in breast cancer cells was more effective than in normal cells, with regard to both the amount of internalized material and the achievement of more strategic intracellular distribution. Moreover, this process occurred through a clathrin-dependent endocytosis pathway with different basal expression levels of this protein in the cell lines tested.

First PET Imaging Studies With 63Zn-Zinc Citrate in Healthy Human Participants and Patients With Alzheimer Disease.

Abnormalities in zinc homeostasis are indicated in many human diseases, including Alzheimer disease (AD). 63Zn-zinc citrate was developed as a positron emission tomography (PET) imaging probe of zinc transport and used in a first-in-human study in 6 healthy elderly individuals and 6 patients with clinically confirmed AD. Dynamic PET imaging of the brain was performed for 30 minutes following intravenous administration of 63Zn-zinc citrate (∼330 MBq). Subsequently, body PET images were acquired. Urine and venous blood were analyzed to give information on urinary excretion and pharmacokinetics. Regional cerebral 63Zn clearances were compared with 11C-Pittsburgh Compound B (11C-PiB) and 18F-fluorodeoxyglucose (18F-FDG) imaging data. 63Zn-zinc citrate was well tolerated in human participants with no adverse events monitored. Tissues of highest uptake were liver, pancreas, and kidney, with moderate uptake being seen in intestines, prostate (in males), thyroid, spleen, stomach, pituitary, and salivary glands. Moderate brain uptake was observed, and regional dependencies were observed in 63Zn clearance kinetics in relationship with regions of high amyloid-ß plaque burden (11C-PiB) and 18F-FDG hypometabolism. In conclusion, zinc transport was successfully imaged in human participants using the PET probe 63Zn-zinc citrate. Primary sites of uptake in the digestive system accent the role of zinc in gastrointestinal function. Preliminary information on zinc kinetics in patients with AD evidenced regional differences in clearance rates in correspondence with regional amyloid-ß pathology, warranting further imaging studies of zinc homeostasis in patients with AD.

Optimization of a Dicarboxylic Series for in Vivo Inhibition of Citrate Transport by the Solute Carrier 13 (SLC13) Family.

Inhibition of the sodium-coupled citrate transporter (NaCT or SLC13A5) has been proposed as a new therapeutic approach for prevention and treatment of metabolic diseases. In a previous report, we discovered dicarboxylate 1a (PF-06649298) which inhibits the transport of citrate in in vitro and in vivo settings via a specific interaction with NaCT. Herein, we report the optimization of this series leading to 4a (PF-06761281), a more potent inhibitor with suitable in vivo pharmacokinetic profile for assessment of in vivo pharmacodynamics. Compound 4a was used to demonstrate dose-dependent inhibition of radioactive [(14)C]citrate uptake in liver and kidney in vivo, resulting in modest reductions in plasma glucose concentrations.

Pharmacokinetics of centhaquin citrate in a rat model.

OBJECTIVE: Centhaquin citrate is a novel agent being developed for use in the treatment of haemorrhagic shock. It has decreased mortality in rat, rabbit and pig models of hypovolaemic shock compared to hypertonic saline and lactated Ringer's resuscitation. The pharmacokinetics of centhaquin citrate have not been described to date. METHODS: Sixteen male Sprague Dawley rats were given an intravenous bolus of 0.45 mg/kg centhaquin citrate. Rats were divided into two groups; plasma concentrations were measured at five time points for each group within 24 h after administration. Competing compartmental pharmacokinetic models were assessed. The nonparametric adaptive grid function within the Pmetrics package for R was used for parameter estimation. Predicted concentrations were calculated using population median and individual Bayesian posterior parameters. KEY FINDINGS: A two-compartment model of centhaquin citrate best fit the data. Median (IQR) values for elimination coefficient (Ke), volume of distribution (V) and intercompartmental transfer rates (Kcp, Kpc) were 8.8 (5.2-12.8) h(-1), 6.4 (2.8-10.4) l, 11.9 (4.6-15.0) h(-1) and 3.7 (2.3-9.1) h(-1), respectively. CONCLUSION: This is the first report of the pharmacokinetic parameters of centhaquin citrate in a rat model. Centhaquin citrate was found to have a short half-life with a large volume of distribution.

Comparative pharmacokinetics of gastrodin in rats after intragastric administration of free gastrodin, parishin and Gastrodia elata extract.

ETHNOPHARMACOLOGICAL RELEVANCE: Gastrodia elata Blume, a traditional Chinese herb, was widely used against convulsant, vertigo, paralysis, epilepsy, tetanus, asthma and immune dysfunctions. Gastrodin is one of the major bioactive components of G. elata and it is known for its anticonvulsive, anti-inflammatory, antiepileptic and neuroprotective effects. MATERIALS AND METHODS: An ultra high performance liquid chromatography-fluorescence detection (UHPLC-FLD) method was developed to determine gastrodin in rat plasma. Gastrodin and Thiamphenicol (internal standard, IS) were extracted from rat plasma by immediately protein precipitation. The pharmacokinetics of gastrodin in rats by following differently administered types was studies: intragastric administration of gastrodin (100mg/kg), parishin (116 mg/kg, with the same mole of gastrodin moiety) and G. elata extract (2.3g/kg, with the same mole of gastrodin moiety). Non-compartmental pharmacokinetic profiles were constructed using the software of WinNonlin (Phoenix, version 6.3), and the pharmacokinetic parameters were compared using unpaired Student's t-test. RESULTS: The results showed that the pharmacokinetic parameters, including Cmax, Tmax, AUC0-∞, t1/2, MRT, Vd, CL, were quite different among the three types of gastrodin administration. The administration of parishin and G. elata extract, which either could convert to gastrodin in vivo or contained free gastrodin and abundant gastrodin conjugates, gave rise to higher elimination half-life (t1/2) and mean residence time (MRT) values for gastrodin compared to free gastrodin administered. CONCLUSION: The comparison of the pharmacokinetics of gastrodin among three different administered types of gastrodin in rats suggested that administration of parishin or G. elata extract in clinic may result in a longer duration time of action than that of the administration of free gastrodin. The results may provide some guidance for the clinical applications of parishin and G. elata.

Extramedullary Soft Tissue Involvement and Discrepant Osseous Uptake on Tc-99m MDP and Ga-67 Citrate Scintigraphy in a Patient With Multiple Myeloma: A Case Report and Literature Review.

Multiple myeloma (MM) is a plasma cell neoplasm with skeletal destruction which could also spread to extramedullary regions. Common diagnostic imaging modalities include skeletal radiography, computed tomography (CT), magnetic resonance imaging (MRI). Recently, PET/CT is proposed as an ideal tomographic tool for diagnosis and follow-up, but impending factors includes high cost, limited availability of cameras and radiotracers. Bone scan and gallium scan are usually considered of limited clinical value. Herein, we present a 66-year-old Taiwanese man with MM, who was hospitalized to our hospital for bone pain control. Bone and gallium scintigraphies were obtained for bone pain and infection workup. However, unexpected features of discordant osseous uptake with high gallium-to-bone uptake ratio and extramedullary gallium uptake were noted which both indicated poor prognosis of MM. The patient then passed away due to rapid disease progression. In conclusion, although gallium and bone scintigraphies are considered less sensitive for MM, combined use may be a good alternative for 18F-FDG PET/CT in evaluation of disease extent and prognosis, especially in high-risk patients or with suspicion of disease progression.