Population analysis of the non-linear red blood cell partitioning of draflazine following various infusion durations

Objective: The pharmacokinetics and non-linear red blood cell partitioning of the nucleoside transport inhibitor draflazine were investigated in 19 healthy male and female subjects (age range 22–55 years) after a 15-min i.v. infusion of 1 mg, immediately followed by infusions of variable rates (0.25, 0.5 and 1 mg · h⁻¹) and variable duration (2–24 h). Methods: The parameters describing the capacity-limited specific binding of draflazine to the nucleoside transporters located on erythrocytes were determined by NONMEM analysis. The red blood cell nucleoside transporter occupancy of draflazine (RBC occupancy) was evaluated as a pharmacodynamic endpoint. Results: The population typical value for the dissociation constant K _d (%CV) was 0.648 (12) ng · ml⁻¹ plasma, expressing the very high affinity of draflazine for the erythrocytes. The typical value of the specific maximal binding capacity B_max (%CV) was 155 (2) ng · ml⁻¹ RBC. The interindividual variability (%CV) was moderate for K _d (38.9%) and low for B_max (7.8%). As a consequence, the variability in RBC occupancy of draflazine was relatively low, allowing the justification of only one infusion scheme for all subjects. The specific binding of draflazine to the red blood cells was a source of non-linearity in draflazine pharmacokinetics. Steady-state plasma concentrations of draflazine virtually increased dose-proportionally and steady state was reached at about 18 h after the start of the continuous infusion. The t_1/2βaveraged 11.0–30.5 h and the mean CL from the plasma was 327 to 465 ml · min⁻¹. The disposition of draflazine in whole blood was different from that in plasma. The mean t_1/2β was 30.2 to 42.2 h and the blood CL averaged 17.4–35.6 ml · min⁻¹. Conclusion: Although the pharmacokinetics of draflazine were non-linear, the data of the present study demonstrate that draflazine might be administered as a continuous infusion over a longer time period (e.g., 24 h). During a 15-min i.v. infusion of 1 mg, followed by an infusion of 1 mg · h⁻¹, the RBC occupancy of draflazine was 96% or more. As the favored RBC occupancy should be almost complete, this dose regimen could be justified in patients. Received: 6 February 1997 / Accepted in revised form: 12 May 1997     

In-vitro red blood cell partitioning of doxycycline

Objective:

In-vitro red blood cell (RBC) partitioning of doxycycline was studied to determine whether doxycycline penetrates RBC and its concentration was assayed keeping in view its high lipophilicity.

Materials and Methods:

Standardization of doxycycline was performed in whole blood and plasma of cattle by microbiological assay using Bacillus subtillis ATCC 6633 as indicator organizm. Actual concentration of the drug was obtained by comparing zone inhibition with standard graph and the extent of partitioning was mathematically calculated.

Results:

The R² value of standard graph for doxycycline was 0.9934 and 0.9727 for plasma and whole blood, respectively. Overall, RBC partitioning of doxycycline was found to be 18.40 ± 1.70%.

Conclusions:

Overall RBC partitioning of doxycycline indicated low penetration into RBC. Plasma is the fluid suggested for pharmacokinetic evaluation of doxycycline.     

High-performance liquid chromatographic analysis, plasma protein binding and red blood cell partitioning of phenprobamate

A new high-performance liquid chromatographic procedure for the analysis of phenprobamate, a skeletal muscle relaxant in biologic fluids was developed. The method used a C18 reverse phase column, a mobile phase of methanol/acetonitrile/water (33:15:52), and UV detection at 215 nm. The assay procedure was applied to the determination of phenprobamate binding to rat and human plasma proteins using the equilibrium dialysis method. In addition, the red blood cell/plasma partitioning was determined in the whole blood of rats and humans. Phenprobamate exhibited a moderate binding to plasma proteins of rat (74.3 +/- 2.2 per cent) and human (80.5 +/- 1.1 per cent). The protein binding was concentration-independent in the range of 10 to 80 micrograms ml-1. Phenprobamate binding to plasma proteins was also determined in the presence of 10 micrograms ml-1 acetaminophen. The protein binding of phenprobamate was not significantly altered by acetaminophen (74.4 +/- 0.6 per cent for rat plasma; 75.7 +/- 1.6 per cent for human plasma). The distribution ratios of phenprobamate between the red blood cells and plasma were greater than unity, 1.86 and 1.59 in rat and human, respectively, indicating a preferential partitioning of the drug in the red blood cells.     

Nonlinear relationship between plasma and red blood cell pharmacokinetics of chlorthalidone in man

Plasma concentrations, red blood cell concentrations, and urinary excretion of chlorthalidone were measured after oral administration of single doses of 100 or 200 mg to ten human subjects. The decay of red blood cell concentrations showed a much longer elimination half-life than the terminal plasma decay curve. The in vitrodistribution of chlorthalidone between plasma and erythrocytes was similar to the in vivodistribution curve obtained from patients who were in a steady-state concentration range. A pharmacokinetic model was developed including nonlinear binding of chlorthalidone by the red blood cells, which in detail accounted for the observed time courses of drug in plasma and erythrocytes simultaneously.This work was supported in part by a grant from the Netherlands Foundation for Medical Research (FUNGO).     

尿液潜血检验中尿液分析仪、显微镜红细胞计数的应用效果探究

目的 分析尿液潜血检验中尿液分析仪、显微镜红细胞计数的应用效果.方法 90份进行尿液检验分析患者的尿液标本,分别进行显微镜红细胞计数检验与尿液分析仪检验,观察两种方法的检验结果 ,以显微镜红细胞计数检验结果为金标准,分析尿液分析仪检验的敏感度、特异度、误诊率、漏诊率.结果显微镜红细胞计数检验阳性20例,阴性70例,阳性...     

Population pharmacokinetic and dynamic analysis of the topoisomerase I inhibitor lurtotecan in phase II studies

Population pharmacokinetic-dynamic analysiswas prospectively integrated in a broadphase II program of lurtotecan (GI147211),a novel camptothecin derived topoisomeraseI inhibitor, to determine the populationpharmacokinetic profile in a largerpopulation, to estimate individualpharmacokinetic parameters and toinvestigate relationships with clinicaloutcome. A sparse sampling method wasapplied during course one, which involvedtwo sampling time-points. A Bayesianalgorithm was used to estimate individualpharmacokinetic parameters, in particulartotal plasma clearance (CL) and volume ofdistribution. In total, samples werecollected of 109 (63%) of 173 patients.Pharmacokinetic-dynamic evaluation could becarried out successfully in 85 (78%) ofthe sampled patients. CL of lurtotecanshowed substantial variability (mean 87± 28 L/h) and was of the same magnitudeas in the phase I studies where fullpharmacokinetic curves were used. Residualvariability in the population estimate ofCL was 9.9%. No significant relationshipswere observed between exposure parametersand toxicity nor likelihood of tumorresponse, however the latter relationshipmay well have been obscured by theheterogeneity of the studied population.Prospective implementation of large scalepopulation pharmacokinetic-dynamic analysisis feasible and important to establishwhether interpatient variability in drugexposure is a major determinant of toxicityor activity.     

Indirect detection of anti-acetylcholinesterase compounds in microcolumn liquid chromatography using packed bed reactor with immobilized human red blood cell acetylcholinesterase and choline oxidase

The inhibiting compounds were separated by micro-column liquid chromatography in the mobile phase containing the natural substrate acetylcholine. A home-made packed bed microbioreactor system containing immobilized enzyme acetylcholinesterase (ACHE) in human red blood cell membrane and choline oxidase (CHO) from alcaligenes was used for the post-column conversion of acetylcholine to hydrogen peroxide which was detected by an electrochemical detector. The inhibition effect of the solutes caused a decrease in the acetylcholinesterase activity, a decrease in the formation of hydrogen peroxide and also a decrease in the response corresponding to the concentration of the solutes. The rate of the enzyme regeneration was also recorded. The micro-system was compared with a conventional LC system comprising commercially prepared enzyme reactor. The stability of the enzymes is at least 3 weeks at ambient temperature. The limit of detection depends on biological activity of inhibition and for galanthamine was 1 pmol.     

尿红细胞MCV与RDW测定鉴别血尿来源的性质

目的探讨尿红细胞平均体积（MCV）与红细胞体积分布宽度（RDW）测定在血尿来源诊断中的价值。方法应用SYsmex XE-2100血细胞分析仪测定4O例。肾小球性血尿患者与36例非肾小球性血尿患者的MCV与RDW。结果’肾小球性血尿MCV明显低于非。肾小球性血尿,有显著性差异。肾小球性血尿的RDW明显高于非肾小球性血尿,有显著性差异。结论使用血细胞分析仪测定尿中红细胞MCV及RDW对血尿来源诊断有一定的价值。     

Evaluation of the multipotent character of human adipose tissue-derived stem cells isolated by Ficoll gradient centrifugation and red blood cell lysis treatment

In the present study, the multipotent potential of two differential isolated human adipose-derived stem cell (hADSC) populations was evaluated. More specifically, hADSC isolated by means of classical Ficoll (F) gradient centrifugation were compared to hADSC isolated by means of red blood cell (RBC) lysis treatment and subsequent cultivation as 3D spheres.No significant difference in the genotypic expression of the multipotent markers Oct-4, Sox-2, Nanog, Klf-4 and cMyc could be observed between both isolation methods. Upon adipogenic and osteogenic differentiation, both hADSC populations showed lipid droplet accumulation and mineral deposition, respectively. Although, a more pronounced mineral deposition was observed in hADSC-RBC, suggesting a higher osteogenic potential. Upon exposure to keratinogenic media, both hADSC populations expressed the keratinocyte markers filaggrin and involucrin, evidencing a successful keratinogenic differentiation. Yet, no differences in expression were observed between the distinctive isolation procedures. Finally, upon exposure to neurogenic differentiation media, a significant difference in marker expression was observed. Indeed, hADSC-RBC only expressed vimentin and nestin, whereas hADSC-F expressed vimentin, nestin, NF-200, MBP and TH, suggesting a higher neurogenic potential.In summary, our data suggest that the choice of the most efficient isolation procedure of hADSC depends on the differentiated cell type ultimately required.