Interactions Between Direct Oral Anticoagulants (DOACs) and Antiseizure Medications: Potential Implications on DOAC Treatment.

The use of direct oral anticoagulants (DOACs) is increasing because of their superior efficacy and safety compared with vitamin K antagonists. Pharmacokinetic drug interactions, particularly those involving cytochrome P450- mediated metabolism and P-glycoprotein transport, significantly affect the efficacy and safety of DOACs. In this article, we assess the effects of cytochrome P450- and P-glycoprotein-inducing antiseizure medications on DOAC pharmacokinetics in comparison to rifampicin. Rifampicin decreases to a varying extent the plasma exposure (area under the concentration-time curve) and peak concentration of each DOAC, consistent with its specific absorption and elimination pathways. For apixaban and rivaroxaban, rifampicin had a greater effect on the area under the concentration-time curve than on peak concentration. Therefore, using peak concentration to monitor DOAC concentrations may underestimate the effect of rifampicin on DOAC exposure. Antiseizure medications that are cytochrome P450 and P-glycoprotein inducers are commonly used with DOACs. Several studies have observed a correlation between the concomitant use of DOACs and enzyme-inducing antiseizure medications and DOAC treatment failure, for example, ischemic and thrombotic events. The European Society of Cardiology recommends avoiding this combination, as well as the combination of DOACs with levetiracetam and valproic acid, owing to a risk of low DOAC concentrations. However, levetiracetam and valproic acid are not cytochrome P450 or P-glycoprotein inducers, and the implications of their use with DOACs remain to be elucidated. Our comparative analysis suggests DOAC plasma concentration monitoring as a possible strategy to guide dosing owing to the predictable correlation between DOACs' plasma concentration and effect. Patients taking concomitant enzyme-inducing antiseizure medications are at risk for low DOAC concentrations and subsequently, treatment failure and thus can benefit from DOAC concentration monitoring to prophylactically identify this risk.