[Direct oral anticoagulants and drug-drug interactions]

Vitamin K antagonists (VKA) top the list of drugs with most drug and dietary interactions and they are among the medications with the highest incidence of life-threatening events. The new direct oral anticoagulants (DOACs) have been developed to overcome many of the disadvantages of a VKA therapy. Especially, fewer clinically significant drug interactions have been reported to date. However, a number of interactions must be considered. These interactions are linked to the DOAC's specific metabolic pathways. The results of these interactions are changes of the DOAC plasma levels leading either to a higher bleeding risk or to a lower therapeutic efficacy. It is known that patients on VKA and on concomitant polymedication show a higher risk of bleeding. Polymedication is more often found in elderly patients. Patients in this population also have more often an indication for an anticoagulant therapy. Various medications are known to lead to an impaired platelet function. An increase of the bleeding risk in case of a platelet function disorder when additionally taking a DOAC is very likely. Therefore, careful consideration of side effects of both DOAC and concomitant medication when prescribing an anticoagulant therapy is mandatory.