抄録
The direct oral anticoagulant dabigatran (D) requires no routine therapeutic monitoring. Yet, drug interactions may increase its inherent bleeding risk, especially in the elderly. We aimed to evaluate to what extent co-prescription of P-gp antagonists with D may increase its plasma levels and lead to bleedings in usual conditions of care.
Methods: Elderly patients from Nice University Medical Center receiving D were included consecutively. Prescriptions were screened for P-gp antagonists (Group A: verapamil, ketoconazole, amiodarone, dronedarone, diltiazem...), whereas control patients (Group B) had no such co-prescription. Blood concentrations of D were measured by HPLC-tandem mass spectrometry (LOQ 1 ng/ml).
Results: 119 consecutive patients (64 males, 55 females) at steady state were sampled for D residual concentrations. Their mean age was 83 +/- 7 years, CHA2DS2Vasc 4.4 +/- 1.7, and MDRD 81 +/- 25 ml/min. Patients co-prescribed with a P-gp antagonist (Group A: 5 verapamil, 4 diltiazem and 39 amiodarone) had higher D concentrations (174 +/- 145 ng/ml), as compared with the 71 patients of group B (113 +/- 81 ng/ml). No difference occurred in bleeding rate (A 11/48: 23%, B 13/71: 18%, p = 0.64). Though, patients presenting with bleeding in group A had significantly higher D concentrations (338 +/- 177 ng/ml) as compared with bleeding patients from group B (100 +/- 70 ng/ml, p<0.03).
Conclusion: Despite higher concentrations of D when co-prescribed with P-gp antagonists in elderly patients, the bleeding occurrence is comparable in usual conditions of clinical use. This may pertain to complex dabigatran PK/PD relationship.
