Innovative approach to Blood sampling using dried Blood spots. application to Pharmacokinetics and Cytochrome P450 Phenotyping

InnovAtIve APProAch to Blood sAmPlIng usIng drIed Blood sPots. APPlIcAtIon to PhArmAcokInetIcs And cytochrome P450 PhenotyPIng M. Bosilkovska; J. Deglon; A. Thomas; C. Samer; J. Desmeules; and Y. Daali Geneva University Hospitals, Geneva, Switzerland; and University Center of Legal Medicine, Lausanne-Geneva, Switzerland Background: The use of dried blood spots (DBS) has gained in popularity in the last few years over conventional whole blood or plasma sampling for PK or drug monitoring. In order to overcome the impact that haematocrit has on the spreading of the applied drop of blood, precise knowledge of the collected volume is crucial for the determination of drug/metabolites concentrations. Material and Methods: Although the collection of an accurate capillary volume using a volumetric micropipette is simpler than venous blood collection, it still needs to be conducted by trained technicians using dedicated instruments. To simplify this process a new capillary blood collection device has been developed. The prototype integrates a patented microfluidic plate (WO/2013/144743) allowing for accurate volume control and a conventional filter paper card for blood storage. The concentrations and pharmacokinetic profiles of a P-glycoprotein (P-gp) and six cytochrome P450 (CYP) probes and their metabolites obtained with the new sampling device have been compared with a conventional volumetric micropipetting method in a clinical trial including 30 volunteers who have received the Geneva cocktail for CYP and P-gp phenotyping. The quantification was done using a previously validated LC/MS-MS method. Results: Concentrations obtained with the new microfluidic sampling device showed excellent correlation with conventional micropipetting concentrations with slopes values close to 1 (0.91 – 1.03) and determination coefficients R> 0.90 for all of the 13 analysed substances. Sampling could be successfully performed by the volunteers themselves with almost no previous training. Conclusion: DBS technique combined with an innovative sampling device and a sensitive analytical method can be used as a self-test for CYP and P-gp phenotyping The use of this technique can be further enlarged to the quantification of other substances for PK studies and therapeutic drug monitoring.