Pharmacokinetic Interpretation Research Articles

Pharmacokinetic Interpretation of Applying Local Drug Delivery System for the Treatment of Deep Surgical Site Infection in the Spine.

Surgical site infections (SSIs) after spinal surgery present significant challenges, including poor antibiotic penetration and biofilm formation on implants, leading to frequent treatment failures. Polymethylmethacrylate (PMMA) is widely used for localized drug delivery in bone infections, yet quantifying individual drug release kinetics is often impractical. This retrospective study analyzed 23 cases of deep SSIs (DSSIs) following spinal surgery treated with antibiotic-loaded PMMA. A mathematical model estimated personalized drug release kinetics from PMMA, considering disease types, pathogens, and various antibiotics. The study found that vancomycin (VAN), ceftriaxone (CRO), and ceftazidime (CAZ) reached peak concentrations of 15.43%, 15.42%, and 15.41%, respectively, within the first two days, which was followed by a lag phase (4.91-4.92%) on days 2-3. On days 5-7, concentrations stabilized, with CRO at 3.22% and CAZ/VAN between 3.63% and 3.65%, averaging 75.4 µg/cm2. Key factors influencing release kinetics include solubility, diffusivity, porosity, tortuosity, and bead diameter. Notably, a patient with a low glomerular filtration rate (ASA IV) was successfully treated with a shortened 9-day intravenous VAN regimen, avoiding systemic complications. This study affirms the effectiveness of local drug delivery systems (DDS) in treating DSSIs and underscores the value of mathematical modeling in determining drug release kinetics. Further research is essential to optimize release rates and durations and to mitigate risks of burst release and tissue toxicity.

An alternative biomimetic tool – Dual hydrophilic/reversed-phase interaction mode

During the early stages of drug discovery, it becomes increasingly important to acquire a basic physico-chemical and pharmacokinetic profile of drug candidates using efficient and cost-effective laboratory and computational models. In this study, the possibility of applying the dual hydrophilic interaction liquid chromatography/reversed-phase mode (HILIC/RP) as a alternative biomimetic tool for the preliminary profiling of imidazoline and piperazine-related compounds was investigated. Their retention behaviour on the mixed-mode HILIC/RP column was described as a dependence of the logarithm of the retention factor (logk) in relation to the volume fraction of the water component in the mobile phase (φ). The retention was quantified by integration of HILIC (logkH), RP (logkR) and the total HILIC/RP (logkA) area under the logk = f(φ) curve. The biomimetic capabilities of HILIC/RP mode were observed through physico-chemical and pharmacokinetic interpretation of chromatographic behaviour. The physico-chemical characteristics of the HILIC/RP mode were defined based on linear solvation energy relationships, genetic algorithm-multiple linear regression and Boruta-XGBoost predictive modeling. The created models showed reliable predictive performances for defining the logkA, logkR, and logkH values. The mixed-mode logkA, logkR, and logkH parameters correlate well with physico-chemical (e.g., lipophilicity indices) and basic pharmacokinetic properties of the examined compounds. The models created have confirmed that the simultaneous contribution of both HILIC/RP mechanisms can be used to accurately evaluate the key properties of newly synthesized imidazoline and piperazine-related compounds while reducing costs and selecting suitable candidates in the early stages of drug development and discovery.

Efavirenz-Based Antiretroviral Therapy but Not Pregnancy Increased Unbound Piperaquine Exposure in Women during Malaria Chemoprevention.

Dihydroartemisinin-piperaquine (DP) is highly effective for malaria chemoprevention during pregnancy, but the standard dosing of DP that is used for nonpregnant adults may not be optimal for pregnant women. We previously reported that the pharmacokinetic exposure of total piperaquine (PQ; both bound and unbound to plasma proteins) is reduced significantly in the context of pregnancy or efavirenz (EFV)-based antiretroviral therapy (ART). However, as PQ is >99% protein-bound, reduced protein binding during pregnancy may lead to an increase in the pharmacologically active unbound drug fraction (fu), relative to the total PQ. We investigated the impact of pregnancy and EFV use on the fu of PQ to inform the interpretation of pharmacokinetics. Plasma samples from 0 to 24 h after the third (final) DP dose were collected from pregnant women at 28 weeks gestation who were receiving or not receiving EFV-based ART as well as from women 34 to 54 weeks postpartum who were not receiving EFV-based ART, who served as controls. Unbound PQ was quantified via ultrafiltration and liquid chromatography-tandem mass spectrometry, with fu being calculated as PQunbound/PQtotal. The geometric mean fu did not differ between pregnant and postpartum women (P = 0.66), but it was 23% (P < 0.01) greater in pregnant women receiving EFV-based ART, compared to that in postpartum women who were not receiving EFV-based ART. The altered drug-protein binding, potentially due to the displacement of PQ from plasma proteins by EFV, resulted in only a 14% lower unbound PQ exposure (P = 0.13) in the presence of a 31% lower total PQ exposure (P < 0.01), as estimated by the area under the concentration time curve from 0 to 24 h post-last dose in pregnant women who were receiving EFV-based ART. The results suggest that the impact of pregnancy and EFV-based ART on the exposure and, in turn, the efficacy of PQ for malaria prevention may not be as significant as was suggested by the changes in the total PQ exposure. Further study during the terminal elimination phase (e.g., on day 28 post-dose) would help better characterize the unbound PQ exposure during the full dosing interval and, thus, the overall efficacy of PQ for malaria chemoprevention in this special population.

Comparing Salivary Caffeine Kinetics of 13C and 12C Caffeine for Gastric Emptying of 50 mL Water.

Gastric water emptying as a critical parameter for oral drug absorption can be investigated by several imaging techniques or by the interpretation of pharmacokinetics of appropriate substances. Recently introduced salivary caffeine kinetics is a valuable tool, but the required caffeine abstinence limits its applicability. To avoid the caffeine abstinence, stable isotope-labeled caffeine might be used, but the representability and transferability of kinetics for evaluation of gastric emptying must be demonstrated. Thus, salivary caffeine pharmacokinetics were compared for naturally occurring 12C-caffeine and 13C3-caffeine after the administration of water under fasting conditions in six healthy young subjects. For this purpose, an ice capsule containing the two caffeine species was administered with 50 mL tap water. Gastric water emptying was simultaneously quantified using magnetic resonance imaging (MRI). Gastric emptying of 50 mL of water could be successfully evaluated. The salivary caffeine kinetics of 13C3- and 12C-caffeine were nearly congruent and showed good linear correlations in all subjects, with a mean correlation coefficient of 0.96 in pooled data. Thus, the substitution of natural 12C caffeine with stable isotope-labeled 13C3-caffeine offers the opportunity for broader application of the salivary caffeine gastric emptying technique and increases the robustness of the method against environmental contamination with caffeine.

Specific Gene Duplication and Loss of Cytochrome P450 in Families 1-3 in Carnivora (Mammalia, Laurasiatheria).

Simple SummaryIn this study we investigated the specific duplication and loss events of cytochrome P450 (CYP) genes in families 1-3 in Carnivora. These genes have been recognized as essential detoxification enzymes, and, using genomic data, we demonstrated a synteny analysis of the CYP coding cluster and a phylogenetic analysis of these genes. We discovered the CYP2Cs and CYP3As expansion in omnivorous species such as the badger, the brown bear, the black bear, and the dog. Furthermore, phylogenetic analysis revealed the evolution of CYP2Cs and 3As in Carnivora. These findings are essential for the appropriate estimation of pharmacokinetics or toxicokinetic in wild carnivorans.Cytochrome P450s are among the most important xenobiotic metabolism enzymes that catalyze the metabolism of a wide range of chemicals. Through duplication and loss events, CYPs have created their original feature of detoxification in each mammal. We performed a comprehensive genomic analysis to reveal the evolutionary features of the main xenobiotic metabolizing family: the CYP1-3 families in Carnivora. We found specific gene expansion of CYP2Cs and CYP3As in omnivorous animals, such as the brown bear, the black bear, the dog, and the badger, revealing their daily phytochemical intake as providing the causes of their evolutionary adaptation. Further phylogenetic analysis of CYP2Cs revealed Carnivora CYP2Cs were divided into CYP2C21, 2C41, and 2C23 orthologs. Additionally, CYP3As phylogeny also revealed the 3As’ evolution was completely different to that of the Caniformia and Feliformia taxa. These studies provide us with fundamental genetic and evolutionary information on CYPs in Carnivora, which is essential for the appropriate interpretation and extrapolation of pharmacokinetics or toxicokinetic data from experimental mammals to wild Carnivora.

Ligand binding at the protein–lipid interface: strategic considerations for drug design

Many drug targets are embedded within the phospholipid bilayer of cellular membranes, including G protein-coupled receptors, ion channels, transporters and membrane-bound enzymes. Increasing evidence from biophysical and structural studies suggests that many small-molecule drugs commonly associate with these targets at binding sites at the protein-phospholipid interface. Without a direct path from bulk solvent to a binding site, a drug must first partition in the phospholipid membrane before interacting with the protein target. This membrane access mechanism necessarily affects the interpretation of potency data, structure-activity relationships, pharmacokinetics and physicochemical properties for drugs that target these sites. With an increasing number of small-molecule intramembrane binding sites revealed through X-ray crystallography and cryogenic electron microscopy, we suggest that ligand-lipid interactions likely play a larger role in small-molecule drug action than commonly appreciated. This Perspective introduces key concepts and drug design considerations to aid discovery teams operating within this target space, and discusses challenges and future opportunities in the field.

BIOANALYSIS METHOD DEVELOPMENT AND VALIDATION OF SMALL MOLECULES IN PHARMACEUTICAL INDUSTRY: A BIOANALYST REVIEW POINT

The focus of bioanalysis employed for the quantitative determination of an active analyte(s) and their metabolite(s) in the biological matrix such as plasma, serum, blood, cerebrospinal fluid, and tissues. The extraction of analyte and metabolite in the biological fluids is carried out using different separation methods such as protein precipitation, liquid-liquid extraction, and solid phase extraction. Bioanalytical method development and validation in the pharmaceutical industry are to provide an assessment and interpretation of pharmacokinetics, pharmacodynamics, toxicokinetics, bioavailability/bioequivalence, and therapeutic drug monitoring relationships. This review paper aims to provide a simple and accurate scientific background to improve the quality for development and validation of a bioanalytical method for small molecules with industrial technique as per regulatory agency requirements (United States Food and Drug Administration, EMEA, International Council for Harmonisation and ANVISA).

Principios de estadística Bayesiana y su relación con la farmacocinética aplicada

La metodología estadística Bayesiana permite, si se conoce la probabilidad poblacional de que un suceso ocurra, modificar su valor cuando se dispone de nueva información individual. Aunque las metodologías Bayesiana y frecuentista (clásica) tienen idénticos campos de aplicación, la primera se aplica cada vez más en investigación científica y análisis de big data. En la farmacoterapia moderna, la farmacocinética clínica ha sido responsable de la expansión de la monitorización, facilitada por desarrollos técnico-analíticos y matemático-estadísticos. La farmacocinética poblacional ha permitido identificar y cuantificar las características fisiopatológicas y de tratamiento en una población de pacientes determinada, en particular en pediatría y neonatología, y otros grupos vulnerables, explicando la variabilidad farmacocinética interindividual. Asimismo, la estimación Bayesiana resulta importante como herramienta estadística aplicada en programas informáticos de optimización farmacoterapéutica cuando la monitorización farmacológica se basa en la interpretación farmacocinética clínica. Aunque con ventajas y limitaciones, la optimización farmacoterapéutica basada en la estimación Bayesiana es cada vez más usada en la actualidad, siendo el método de referencia. Esto es particularmente conveniente para la práctica clínica de rutina debido al limitado número de muestras requeridas por parte del paciente, y a la flexibilidad en cuanto a los tiempos de muestreo de sangre para cuantificación de fármacos. Así, la aplicación de los principios Bayesianos a la práctica de la farmacocinética clínica resulta en la mejora de la atención farmacoterapéutica.

Flow Rate and Apparent Volume of Cerebrospinal Fluid in Rhesus Macaques (Macaca mulatta) Based on the Pharmacokinetics of Intrathecally Administered Inulin.

Cerebrospinal fluid (CSF) flow rate and volume are fundamental to the design and interpretation of preclinical pharmacokinetics and pharmacodynamics studies in NHP. To determine the values of CSF flow rate and volume, we evaluated the plasma and CSF pharmacokinetics of inulin, an inert polysaccharide tracer, in 5 rhesus macaques with CSF ventricular res- ervoirs and lumbar ports; these reservoirs and ports facilitate humane intrathecal administration and serial CSF sampling in unanesthetized macaques. Inulin was administered intrathecally via the CSF ventricular reservoir (n = 3), followed by the collection of lumbar CSF via the lumbar port and plasma. The contribution of dietary inulin was evaluated by using pre- and postprandial inulin plasma concentrations (n = 2) and a feed analysis of the NHP diet. Inulin concentrations were quantified using ELISA. Pharmacokinetic parameters were calculated by using noncompartmental methods. Daily diet was analyzed for inulin by using Official Method no. 997.08 of AOAC International. In male rhesus macaques, the mean CSF flow rate, established via inulin clearance after IT administration, was 0.018 ± 0.003 mL/min; mean CSF volume, established based on apparent volume of distribution, was 10.17 ± 0.63 mL. In plasma, inulin was quantifiable in all pre-administration samples and increased over the sampling period, precluding interpretation of plasma pharmacokinetics. Evaluation of the effect of diet on plasma concentrations established quantifiable inulin levels that showed minimal variation relative to the prandial state. Analysis of the feed detected 5 inulin types ranging from 1100 to 1440 mg per100 g. The diet was the source of detectable pre-administration inulin plasma concentrations, whereas inulin was not detected in CSF before inulin administration.

Principles of Bayesian statistics and its relationship with applied pharmacokinetics

If one knows the probability of an event occurring in a population, Bayesian statistics allows mo difying its value when there is new individual information available. Although the Bayesian and frequentist (classical) methodologies have identical fields of application, the first one is increasin gly applied in scientific research and big data analysis. In modern pharmacotherapy, clinical phar macokinetics has been used for the expansion of monitoring, facilitated by technical-analytical and mathematical-statistical developments. Population pharmacokinetics has allowed the identification and quantification of pathophysiological and treatment characteristics in a specific patient popu lation, especially in the pediatric and neonatal population and other vulnerable groups, explaining interindividual variability. Likewise, Bayesian estimation is important as a statistical tool applied in pharmacotherapy optimization software when pharmacological monitoring is based on clinical phar macokinetic interpretation. With its advantages and despite its limitations, pharmacotherapeutic op timization based on Bayesian estimation is increasingly used, becoming the reference method today. This characteristic is particularly convenient for routine clinical practice due to the limited number of samples required from the patient and the flexibility it shows regarding blood sampling times for drug quantification. Therefore, the application of Bayesian principles to the practice of clinical phar macokinetics has led to the improvement of pharmacotherapeutic care.

&lt;p&gt;A Systematic Review of Vancomycin Dosing in Patients with Hematologic Malignancies or Neutropenia&lt;/p&gt;

ObjectiveTo provide a comprehensive review of vancomycin dosing in patients with hematologic malignancies or neutropenia.MethodsPubMed, Embase and the Cochrane Library were searched through April 2, 2020. Original studies relevant to vancomycin dosing regimen in adults with hematologic malignancies or neutropenia were included. No restriction was applied in study design and language. A descriptive analysis was performed.ResultsTwenty-three studies were included eventually, of which eighteen were case series studies, four were cohort studies and another one was a randomized controlled trial. Five case series studies made a clinical audit of conventional vancomycin dosing in patients with malignancies or neutropenia, showing that the proportion of patients with sub-therapeutic trough levels remained high, ranging from 32% to 88%. Seven case series studies and four cohort studies demonstrated that vancomycin clearance (CLva) tended to be higher in patients with hematologic malignancies or neutropenia, whereas volume of distribution (V) seemed to be comparable to the control group. Five studies proposed individualized initial dosing regimen per the pharmacokinetic changes; however, no prospective validation has been conducted in clinical setting. Additionally, four case series studies suggested that the correlation between vancomycin clearance and estimated creatinine clearance was relatively poor, bringing a great challenge to proper dosing strategy. A randomized controlled trial stated that therapeutic drug monitoring (TDM) of vancomycin could decrease the incidence of nephrotoxicity in immunocompromised febrile patients with hematologic malignancies.ConclusionThe available evidence indicates that conventional vancomycin dosing leads to suboptimal concentration in patients with hematologic malignancy or neutropenia. TDM accompanied by pharmacokinetic interpretation can decrease the risk of nephrotoxicity. The individualization of the initial dosing regimen and mechanisms of augmented clearance require further research.

A Review on the Pharmacokinetic Properties of Naringin and Its Therapeutic Efficacies in Respiratory Diseases.

Flavonoids are an important class of phytopharmaceuticals in plants. Naringin (naringenin- 7-O-rhamnoglucoside) is a flavanone glycoside isolated from folk herbal medicine Exocarpium Citri grandis (called Huajuhong in Chinese). Massive experimental works have been performed on naringin describing its phytochemical, pharmacokinetic, and bioactive properties. Naringin was found to possess multiple pharmacological activities in relieving inflammation, diabetes, neurodegeneration, cardiovascular disorders, and metabolic syndrome. Recently, it has been approved as a potential antitussive and expectorant for clinical trials. However, the pharmacokinetic aspects of naringin and its therapeutic potentials in respiratory diseases have not been comprehensively reviewed. The present review provides highlights of naringin with respect to its absorption, distribution, metabolism, excretion and its therapeutic effects on cough, phlegm, and pulmonary inflammation. This review would be helpful for the interpretation of pharmacokinetics and pharmacodynamics of naringin in clinical trials.

A multiple methods approach to determine adherence with prescribed mycophenolate in children with kidney transplant.

The aim of this study was, to use a multiple methods approach, including, for the first time, dried blood spot (DBS) sampling with population pharmacokinetic interpretation, to assess adherence to mycophenolate in children with kidney transplant. A second aim was to identify patient/parental factors that influenced adherence and to link adherence behaviour to clinical outcomes. A convenience sample of 33 children with kidney transplant (age≤18years) who had been prescribed mycophenolate for at least 3months were recruited from participating outpatient clinics in the UK and Jordan. Medication adherence was determined via self-report questionnaires, medication refill data from dispensing records, and via mycophenolic acid concentrations in plasma and DBS samples obtained from children during a clinic visit. Through triangulation of results from the different methodological approaches a total of 12 children (36.4%) were deemed to be nonadherent with their prescribed mycophenolate treatment. Logistic regression analysis indicated that nonadherence was significantly associated with the presence of mycophenolate side effects. Poor adherence was positively linked to measures of poor clinical outcomes (hospitalisation and the need for kidney biopsy). Despite the imperative regarding medication adherence to help prevent organ rejection, a significant proportion of children are not fully adherent with their therapy. Side-effects appear to be an important factor leading to nonadherence. Measurement of mycophenolate in DBS samples, coupled with the use of population pharmacokinetics modelling, was a convenient direct approach to assessing adherence in children with kidney transplant and has the potential to be introduced into routine practice.

Pharmacokinetics, Tissue Distribution, Metabolism, and Excretion of Naringin in Aged Rats.

Aging is an inevitable biological process characterized by the loss of functional capacity and associated with changes in all phases of pharmacokinetic processes. Naringin, a dietary flavanone glycoside, has been proved to be beneficial for the treatment of multiple age-associated chronic diseases. To date, the pharmacokinetic processes of naringin in aged individuals are still unknown. Thus, a rapid resolution liquid chromatography tandem triple quadrupole mass spectrometry (RRLC-QQQ-MS/MS) method was established for the determination of naringin and its metabolite naringenin in rat plasma, urine, feces, and tissue homogenate. The pharmacokinetic parameters were calculated and a higher exposure of naringin and naringenin were observed in aged rats. Naringin and naringenin were mostly distributed in gastrointestinal tract, liver, kidney, lung, and trachea. Furthermore, a total of 39 flavonoid metabolites (mainly glucuronides and sulfates) and 46 microbial-derived phenolic catabolites were screened with ultra-fast liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UFLC-Q-TOF-MS/MS). Naringenin, hippuric acid, and 3-(4’-hydroxyphenyl)propionic acid were predominated metabolites. This study systemically investigated the pharmacokinetics, tissue distribution, metabolism, and excretion of naringin in aged rats, revealing age- and gender-related changes in the in vivo behavior of naringin. These results would be helpful for the interpretation of pharmacokinetics and pharmacodynamics of naringin in aged population.

A Compilation of Serum Concentrations of 12 Antipsychotic Drugs in a Therapeutic Drug Monitoring Setting.

Background:No comprehensive collection of routine therapeutic drug monitoring data for antipsychotic drugs has been published.Methods:In this compilation, data on 12 antipsychotics are presented. The drugs included are amisulpride (n = 506), aripiprazole (n = 1610), clozapine (n = 1189), flupentixol (n = 215), haloperidol (n = 390), olanzapine (n = 10,268), perphenazine (n = 1065), quetiapine (n = 5853), risperidone (n = 3255), sertindole (n = 111), ziprasidone (n = 1235), and zuclopenthixol (n = 691). Because only one sample per patient is included, the number of patients equals the number of samples. For each drug, median serum concentrations as well as that of the 10th and 90th percentiles are given for a range of daily doses. Comparisons are made between males and females, between patients younger than 65 years and 65 years and older, and between those treated with a low and a high dose of each drug. The concentration-to-dose (C/D) ratio is the primary variable used in these comparisons. Coefficients of variation (CVs) for the serum concentrations of each drug within and between subjects are presented.Results:In general, the C/D ratios were higher in females than in males, higher in those 65 years and older than in younger subjects, and lower in those treated with higher doses than in those treated with lower doses. CVs between individuals were larger than within subjects, and the CVs were highest for the drugs with short elimination half-lives.Conclusions:For each antipsychotic drug, the results presented can serve as a reference tool for pharmacokinetic interpretation of the individual patient's serum drug level. The compiled serum concentrations and the C/D ratios can support the physician's decision when individualizing dosing and determining treatment strategies for a specific patient.

Mathematical analysis and drug exposure evaluation of pharmacokinetic models with endogenous production and simultaneous first-order and Michaelis-Menten elimination: the case of single dose.

Drugs with an additional endogenous source often exhibit simultaneous first-order and Michaelis-Menten elimination and are becoming quite common in pharmacokinetic modeling. In this paper, we investigate the case of single dose intravenous bolus administration for the one-compartment model. Relying on a formerly introduced transcendent function, we were able to analytically express the concentration time course of this model and provide the pharmacokinetic interpretation of its components. Using the concept of the corrected concentration, the mathematical expressions for the partial and total areas under the concentration time curve (AUC) were also given. The impact on the corrected concentration and AUC is discussed as well as the relative contribution of the exogenous part in presence of endogenous production. The present findings theoretically elucidate several pharmacokinetic issues for the considered drug compounds and provide guidance for the rational estimation of their pharmacokinetic parameters.

Pseudo-extravasation rate constant of dynamic susceptibility contrast-MRI determined from pharmacokinetic first principles.

Dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) is widely used to obtain informative perfusion imaging biomarkers, such as the relative cerebral blood volume (rCBV). The related post-processing software packages for DSC-MRI are available from major MRI instrument manufacturers and third-party vendors. One unique aspect of DSC-MRI with low-molecular-weight gadolinium (Gd)-based contrast reagent (CR) is that CR molecules leak into the interstitium space and therefore confound the DSC signal detected. Several approaches to correct this leakage effect have been proposed throughout the years. Amongst the most popular is the Boxerman-Schmainda-Weisskoff (BSW) K2 leakage correction approach, in which the K2 pseudo-first-order rate constant quantifies the leakage. In this work, we propose a new method for the BSW leakage correction approach. Based on the pharmacokinetic interpretation of the data, the commonly adopted R2 * expression accounting for contributions from both intravascular and extravasating CR components is transformed using a method mathematically similar to Gjedde-Patlak linearization. Then, the leakage rate constant (KL ) can be determined as the slope of the linear portion of a plot of the transformed data. Using the DSC data of high-molecular-weight (~750kDa), iron-based, intravascular Ferumoxytol (FeO), the pharmacokinetic interpretation of the new paradigm is empirically validated. The primary objective of this work is to empirically demonstrate that a linear portion often exists in the graph of the transformed data. This linear portion provides a clear definition of the Gd CR pseudo-leakage rate constant, which equals the slope derived from the linear segment. A secondary objective is to demonstrate that transformed points from the initial transient period during the CR wash-in often deviate from the linear trend of the linearized graph. The inclusion of these points will have a negative impact on the accuracy of the leakage rate constant, and even make it time dependent.

Development of Cordycepin Formulations for Preclinical and Clinical Studies.

There is extensive literature on in vivo studies with cordycepin, but these studies were generally conducted without validation of the various formulations, especially in terms of the solubility of cordycepin in the dosing vehicles used. Cordycepin is a promising drug candidate in multiple therapeutic areas, and there is a growing interest in studies aimed at assessing the pharmacological activity of this compound in relevant animal disease models. It is likely that many reported in vivo studies used formulations in which cordycepin was incompletely soluble. This can potentially confound the interpretation of pharmacokinetics and efficacy results. Furthermore, the presence of particles in intravenously administered suspension can cause adverse effects and should be avoided. Here, we present the results from our development of simple and readily applicable formulations of cordycepin based on quantitative solubility assessment. Homogeneous solutions of cordycepin were prepared in phosphate-buffered saline (PBS) at different pH levels, suitable as formulations for both intravenously and oral administration. For the purpose of high-dose oral administration, we also developed propylene glycol (PPG)-based vehicles in which cordycepin is completely soluble. The stability of the newly developed formulations was also assessed, as well as the feasibility of their sterilisation by filtration. Additionally, an HPLC-UV method for the determination of cordycepin in the formulations, which may also be useful for other purposes, was developed and validated. Our study could provide useful information for improvement of future preclinical and clinical studies involving cordycepin.

Pharmacokinetics of gene recombined angiogenesis inhibitor Kringle 5 in vivo using 131I specific markers and SPECT/CT

The previous pharmacokinetic methods can be only limited to drug analysis in vitro, which provide less information on the distribution and metabolismof drugs, and limit the interpretation and assessment of pharmacokinetics, the determination of metabolic principles, and evaluation of treatment effect. The objective of the study was to investigate the pharmacokinetic characteristics of gene recombination angiogenesis inhibitor Kringle 5 in vivo. The SPECT/CT and specific 131I-Kringle 5 marked by Iodogen method were both applied to explore the pharmacokinetic characteristics of 131I-Kringle 5 in vivo, and to investigate the dynamic distributions of 131I-Kringle 5 in target organs. Labeling recombinant angiogenesis inhibitor Kringle 5 using 131I with longer half-life and imaging in vivo using SPECT instead of PET, could overcome the limitations of previous methods. When the doses of 131I-Kringle 5 were 10.0, 7.5 and 5.0g/kg, respectively, the two-compartment open models can be determined within all the metabolic process in vivo. There were no significant differences in t1/2α, t1/2β, apparent volume of distribution and CL between those three levels. The ratio of AUC(0~∞) among three different groups of 10.0, 7.5 and 5.0g/kg was 2.56:1.44:1.0, which was close to the ratio (2:1.5:1.0). It could be clear that in the range of 5.0–10.0g/kg, Kringle 5 was characterized by the first-order pharmacokinetics. Approximately 30min after 131I-Kringle 5 was injected, 131I-Kringle 5 could be observed to concentrate in the heart, kidneys, liver and other organs by means of planar imaging and tomography. After 1h of being injected, more radionuclide retained in the bladder, but not in intestinal. It could be concluded that 131I-Kringle 5 is mainly excreted through the kidneys. About 2h after the injection of 131I-Kringle 5, the radionuclide in the heart, kidneys, liver and other organs was gradually reduced, while more radionuclide was concentrated in the bladder. The radionuclide was completely metabolized within 24h, and the distribution of radioactivity in rats was similar to normal levels. In our study, the specific marker 131I-Kringle 5 and SPECT/CT were successfully used to explore pharmacokinetic characteristics of Kringle 5 in rats. The study could provide a new evaluation platform of the specific, in vivo and real-time functional imaging and pharmacokinetics for the clinical application of 131I-Kringle 5.

Evaluation of theophylline therapeutic drug monitoring service

BackgroundTherapeutic monitoring of theophylline serum levels is required due to its narrow therapeutic range and marked interindividual pharmacokinetic variability. We evaluated therapeutic drug monitoring service for theophylline in Slovenian clinical setting, which currently includes no pharmacokinetic evaluation of measured theophylline serum concentrations. MethodsWe retrospectively evaluated 127 randomly selected theophylline serum level determinations performed in 2010 in a tertiary clinical setting in Slovenia. Demographic data, information on theophylline dosing and blood sampling was collected from patients’ data files. Authors evaluated the appropriateness of the following procedures: indications for theophylline serum concentration measurement, timing of blood sampling and dosage adjustments made after theophylline levels had been reported. On the basis of collected data, population pharmacokinetic model for theophylline was built and further used for the evaluation of dosage adjustments. ResultsOut of 127 cases, 107 (84.3%) had clinically justified indication for theophylline serum level measurement. Near half of measurements (44.9%) were performed before the steady state of theophylline concentrations was established. 65% of measured concentrations were subtherapeutic and the average measured concentration was below therapeutic range (53.1 μmol/L). Despite subtherapeutic concentrations the dose of theophylline was mainly not increased. Pharmacokinetic model enabled the calculation of average optimal daily dose which was significantly higher than the average actual daily dose used (876 mg vs. 572 mg, p &lt; 0.001). ConclusionsTheophylline TDM service should be optimized and pharmacokinetic interpretation of theophylline serum levels should be integrated into clinical practice.