NOACs: drug–drug interactions

We commend Fralick and colleagues for their article on drug interactions with rivaroxaban.¹ All novel oral anticoagulants (NOACs) were introduced as at least noninferior (in some cases superior) to warfarin. In addition to high efficacy, NOACs were reported to have a better safety profile with the added advantage of eliminating the requirement for regular coagulation monitoring.²

Despite fewer food interactions, physicians still have to consider drug–drug interactions when prescribing NOACs. These pharmacokinetic interactions were divided into three levels of warnings: red alert precludes the use of a given NOAC (contraindicated/discouraged); orange alert prompts adapting the NOAC dose; and yellow alert allows for maintaining the original dose unless two or more yellow interactions are present — in which case, the NOAC dose may need to be adapted (orange) or the drug not prescribed at all (red). For many potential interactions with medications often used for atrial fibrillation or other comorbidities, no detailed information is available. It is prudent to abstain from using NOACs until more data are available. Clinicians prescribing NOACs must be aware of relevant drug–drug interactions as well as of the limited possibilities to assess the level of anticoagulation. Close collaboration with pharmacists and anticoagulation specialists seems crucial.³

Letters to the editor.

Letters have been abbreviated for print. See www.cmaj.ca for full versions and competing interests.