One in three NOAC users skipping meds

NOACs are viewed as more effective and convenient replacements for warfarin, but there's a surprising downside

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One in three patients prescribed NOACs halt their medication within the first six months of use, increasing their risk of stroke, transient ischaemic attack and death, authors of a study say.

These patients were 75% more likely to have a stroke, TIA or death if they were non-persistent to dabigatran and 89% more likely if they were non-persistent to rivaroxaban, compared with patients who continued their medication.

“Although NOACs are commonly viewed as more effective and convenient replacements for warfarin, NOAC non-persistence in practice may limit the expected benefits,” the study authors wrote.

“Non-persistence” was defined by the researchers as a gap of two weeks or more between prescriptions.

This was considered a clinically meaningful gap in the anticoagulation therapy because both drugs have short half-lives of up to 17 hours, and most patients eliminate 95% or more of the medication within four days.

To study real-world adherence to antithrombotics, the researchers undertook a retrospective cohort study of Canadian prescription data between 1998 and 2014.

Almost 26,000 adults prescribed either dabigatran or rivaroxaban were included in the study.

The US and Canadian researchers found that within six months of drug initiation, one third of patients had gaps of at least a fortnight between their NOAC prescriptions.

In terms of TIA and stroke alone, the risk for dabigatran non-persistence was four times higher, and rivaroxaban non-persistence was six times higher.

Patients were also less likely to restart their medication once they had a gap, with the authors finding more than one in four not going back on to their NOAC.

“We have found higher levels of non-persistence in clinical practice, so it cannot be presumed that these NOACs will be as effective in clinical practice as was found in the landmark clinical trials,” the authors wrote.

One of the drawcards of NOACs was that less clinician contact made them more convenient for patients.

But this might have backfired, the authors said.

“Without close monitoring and follow-up appointments, as is the norm with warfarin, patients taking NOACs in clinical practice may not actively seek an appointment with their healthcare provider to discuss medication intolerance and side effects, which may lead to drug non-persistence,” they wrote.

Bleeding and gastrointestinal side-effects could also be to blame for the medication drop off.

The authors pointed to previous research showing increased monitoring within the first three months of initiation led to greater dabigatran adherence.

“Greater awareness by clinicians of possible dabigatran and rivaroxaban non-persistence, coupled with closer monitoring by anticoagulation clinics and pharmacists may be warranted to prevent premature discontinuation of therapy and associated adverse clinical outcomes,” they concluded.

Heart 2017; online 12 March