Development of an intravenous microdialysis method for pharmacokinetic investigations in humans

Comparison of Intravenous Microdialysis and Standard Plasma Sampling for Monitoring of Vancomycin and Meropenem Plasma Concentrations-An Experimental Porcine Study

Microdialysis is a catheter-based method suitable for dynamic sampling of unbound antibiotic concentrations. Intravenous antibiotic concentration sampling by microdialysis has several advantages and may be a superior alternative to standard plasma sampling. We aimed to compare concentrations obtained by continuous intravenous microdialysis sampling and by standard plasma sampling of both vancomycin and meropenem in a porcine model. Eight female pigs received 1 g of both vancomycin and meropenem, simultaneously over 100 and 10 min, respectively. Prior to drug infusion, an intravenous microdialysis catheter was placed in the subclavian vein. Microdialysates were collected for 8 h. From a central venous catheter, plasma samples were collected in the middle of every dialysate sampling interval. A higher area under the concentration/time curve and peak drug concentration were found in standard plasma samples compared to intravenous microdialysis samples, for both vancomycin and meropenem. Both vancomycin and meropenem concentrations obtained with intravenous microdialysis were generally lower than from standard plasma sampling. The differences in key pharmacokinetic parameters between the two sampling techniques underline the importance of further investigations to find the most suitable and reliable method for continuous intravenous antibiotic concentration sampling.

Simultaneous HPLC analysis of triamcinolone acetonide and budesonide in microdialysate and rat plasma: application to a pharmacokinetic study

A specific and reliable HPLC-PDA method for the quantitative determination of triamcinolone acetonide, budesonide and fluticasone propionate (as internal standards) in small volumes of microdialysate and rat plasma was developed. An efficient solid-phase extraction (SPE) procedure for plasma samples yielded extremely clean extracts with overall recovery of 104.3% and 95.7% for triamcinolone acetonide (TA) and fluticasone propionate, respectively. Plasma extracts obtained after SPE and microdialysis samples were directly injected on a C18 column to separation. The method has been validated with good linearity, sensitivity, specificity and high accuracy (RE -5.28% to 9.14%) and precision (CV 0.50% to 6.62%) on both matrices. In stability studies, TA and budesonide were stable during storage and assay procedures. The method was applied to a pharmacokinetic study in rodents using microdialysis to determine protein unbound TA concentrations in blood and muscle.

Microdialysis based device for continuous extravascular monitoring of blood glucose

Glycemic control of intensive care patients can be beneficial for this patient group but the continuous determination of their glucose concentration is challenging. Current continuous glucose monitoring systems based on the measurement of interstitial fluid glucose concentration struggle with sensitivity losses, resulting from biofouling or inflammation reactions. Their use as decision support systems for the therapeutic treatment is moreover hampered by physiological time delays as well as gradients in glucose concentration between plasma and interstitial fluid. To overcome these drawbacks, we developed and clinically evaluated a system based on microdialysis of whole blood. Venous blood is heparinised at the tip of a double lumen catheter and pumped through a membrane based micro-fluidic device where protein-free microdialysate samples are extracted. Glucose recovery as an indicator of long term stability was studied in vitro with heparinised bovine blood and remained highly stable for 72 h. Clinical performance was tested in a clinical trial in eight healthy volunteers undergoing an oral glucose tolerance test. Glucose concentrations of the new system and the reference method correlated at a level of 0.96 and their mean relative difference was 1.9 +/- 11.2%. Clinical evaluation using Clark's Error Grid analysis revealed that the obtained glucose concentrations were accurate and clinically acceptable in 99.6% of all cases. In conclusion, results of the technical and clinical evaluation suggest that the presented device delivers microdialysate samples suitable for accurate and long term stable continuous glucose monitoring in blood.