Value of quantifying ABC transporters by mass spectrometry and impact on in vitro-to-in vivo prediction of transporter-mediated drug-drug interactions of rivaroxaban.

ABC transporters, such as P-gp and BCRP, are involved in rivaroxaban pharmacokinetics and can lead to drug-drug interactions (DDIs). Investigations of the victim role for rivaroxaban and transporter-mediated DDI are commonly performed using in vitro models. However, interpretation of rivaroxaban efflux transport and DDI studies in cell models may be influenced by P-gp and BCRP transporter abundance. This study aimed to develop an LC-MS/MS quantification method for assessing the relationship between transporter expression and functionality in Caco-2ATCC, Caco-2ECACC, MDCK-MDR1, MDCK-BCRP cell models. First, the relative and absolute quantities of the transporters were determined by LC-MS/MS. P-gp and BCRP expression was then confirmed by western blotting and immunofluorescence staining. Finally, P-gp and BCRP functional activities and half-inhibitory concentrations (IC50s) of two specific inhibitors (verapamil and ko143) were determined by bidirectional transport experiments. P-gp and BCRP protein expression was detected at the cell membrane and was greater in the respective transfected models. Efflux ratios were correlated with P-gp and BCRP quantities. The lowest IC50s were obtained in the MDCK-MDR1 and MDCK-BCRP models for verapamil and ko143, respectively. In conclusion, this study demonstrated that LC-MS/MS can accurately quantify P-gp and BCRP efflux transporters and thereby improve the interpretation of transport data and in vitro-in vivo correlations.

[Analysis of the question-answer activity of a hospital pharmacy. Example of the handling of drug interactions]. / Analyse de l'activité question-réponse d'une pharmacie à usage intérieur. Exemple de la gestion des interactions médicamenteuses.

INTRODUCTION: The medical care of patients generates questions among healthcare professionals. Some will necessitate an advanced research. The hospital pharmacist is at the interface between prescribers, caregivers and the medicines and is requested to answer these requests. Studies conducted in other countries showed that this question-answer activity represents a significant amount of time in daily work. In France, this topic was poorly explored. The objective of our work was to study the volume and the type of questions, the clinical situations, the time required, the medicines implicated and the sources of information used. MATERIALS AND METHODS: A prospective study was conducted in the pharmacy of a university hospital. All the requests answered by the pharmaceutical team, which needed a specific research, analysis and writing of an answer were collected. RESULTS: A hundred and one questions were analyzed, originating from doctors or medicals interns. Almost half concerned drug interactions, and among them, almost a fourth were not mentioned in the Summary of Product Characteristics of the medicines involved. A pharmaceutical advice was provided in 91.5% of the cases. Time dedicated to the research varied between less than 30 minutes and more than 8 hours. DISCUSSION AND CONCLUSION: This study illustrates the question-answer activity of a hospital pharmacy, which is currently not taken into account as an indicator of pharmaceutical activity. A large part concerns analysis and management of drug interactions and requires a significant amount of pharmaceutical time.