The aim of the current study is to evaluate the impact of cytochrome activity and relevant polymorphisms on rivaroxaban/apixaban dosage regimen or treatment efficacy in a hospital setting. The safety issue in this context is particularly relevant, since hospitalisation is linked to a modification of the patient's treatment with often an increase in the number of medications. The resulting changes in metabolism due to modified cytochrome and transporter activities could affect rivaroxaban/apixaban blood concentrations. Our central hypothesis is that genotype and/or phenotype in CYP3A4/5/7 or P-gp may influence the rivaroxaban/apixaban plasma concentration and increase the risk of thrombotic or hemorrhagic events. Thus, investigating how the patient's genotype and/or phenotype for CYP3A4/5/7 and P-gp could potentially alter the bio-disponibility of rivaroxaban and apixaban and therefore the risk to develop adverse events or inefficacy would be of particular interest.