Vitamin K antagonists were hampered by several disadvantages, such as the need for frequent monitoring. In this context, new oral anticoagulants (NOACs) have been developed and are now available on the market. These NOACs, like all anticoagulant drugs, continue to be associated with an increased risk of bleeding. In addition, the lack of antidote and the absence of valid data regarding biological monitoring can pose problems in case of overdose or when emergency surgery is required. Studies investigating the pharmacokinetic properties of rivaroxaban and dabigatran, two NOACs now approved for the market, have shown high variability between individuals, with coefficients of variation of up to 60% for some pharmacokinetic parameters in patients treated after orthopaedic surgery. The relation between plasma concentrations of NOAC and bleeding risk has been clearly established in clinical trials.

Dabigtran, rivaroxaban and apixaban are known substrates of P-glycoprotein (Pgp). Pgp activity can be affected by pharmacological inducing or inhibiting agents. This can lead to a significant change in the pharmacokinetics of NOACs, with a decrease or increase (respectively) in the level of intestinal absorption, leading to respectively reduced or increased plasma concentrations of the drug. Furthermore, there exist genetic mutations of Pgp, presenting in particular a lower level of activity than the non-mutated protein. We hypothesized that the polymorphisms (mutations) of the ABCB1 gene that codes for Pgp could influence plasma concentrations of dabigatran, rivaroxaban and apixaban, and consequently, impact on the concentration of NOACs and as a corollary, on the bleeding and thromboembolic risk of patients treated with these molecules.

The main objective of this study is to study the relation between polymorphisms of the ABCB1 gene that codes for Pgp and plasma concentrations of NOACs in patients treated for a hemorrhagic or thromboembolic complication occurring under NOAC therapy.

Secondary objectives are to evaluate the distribution of ABCB1 polymorphisms among the various hemorrhagic risk factors, and to compare the frequency of the polymorphism in patients from the study population vs the general population.

Inclusion Criteria:

• Patients aged >18 and <80 years of age
• Patients admitted to the University Hospital of Besancon for a serious adverse event (major bleeding complication or thrombo-embolic event) occurring under treatment with any one of the three commercially available new oral anticoagulant agents (rivaroxaban, apixaban or dabigatran).
• Patients must have social security coverage.
• Patients must provide written informed consent.

Exclusion Criteria:

• Hemorrhagic complication from causes not related to drug therapy
• Hemorrhagic complication occurring in patients not treated with oral anticoagulants at the time of the event
• Thrombo-embolic complication occurring in patients not treated with oral anticoagulants at the time of the event
• Legal incapacity, patients under judicial protection
• Patients with no social security coverage
• Patients unlikely to be compliant or anticipated by the investigator to be non-compliant with the study requirements
• Patients in a wash-out period further to participation in a previous clinical trial