November 25, 2015
High NOAC Discontinuation Rate Endangers Atrial
Fibrillation Patients

Toronto—Patients with atrial fibrillation prescribed two novel oral anticoagulants (NOACs) for stroke prevention have dangerously high rates of discontinuation within 6 months, according to a new study.

In fact, according to the presentation at the recent American Heart Association Scientific Sessions in Orlando, one in four patients discontinued dabigatran within 6 months, as did one of three users of rivaroxaban.

University of Toronto researchers and colleagues point out, “There is an association between nonadherence with either dabigatran or rivaroxaban and significantly worse clinical outcomes following medication discontinuation.”

NOACs are more convenient than warfarin, study authors note, yet, their lack of monitoring, and, for dabigatran, dosing frequency may predispose patients to nonadherence. To determine how frequently that occurs, the Canadian researchers conducted a population-based cohort study from April 2012 to March 2014 of AF patients in Ontario, using administrative data of 15,857 dabigatran users and 10,119 rivaroxaban users 65 and older that linked hospital discharge abstract with prescription claims.

In the study, nonadherence was defined as a gap in dabigatran or rivaroxaban prescription for 2 weeks or more within the first 6 months of therapy, and time to discontinuation.

At 6 months, according to the study, 36.5% of patients discontinued dabigatran, while 32.1% of patients discontinued rivaroxaban. Median time to discontinuation was 240 days for dabigatran and 140 days for rivaroxaban.

“Risk of the composite outcome (stroke or death) was significantly higher for those who discontinued dabigatran [HR 1.78 (95% CI 1.62-1.95); p<0.0001] or discontinued rivaroxaban [HR 3.07 (95% CI 2.54-3.72);p<0.0001] compared with those who did not discontinue the medication,” study authors conclude.

Another study presented by some of the same researchers looked at medications for acute myocardial infarction, finding that patients who fail to fill all of their discharge medications increase their risk of dying.

That study looked at 4,591 post-AMI patients older than 65 years. Of 12,832 prescriptions written for them, 73% were filled within 7 days and 79% were filled within 120 days.

Results indicate the adjusted 1-year mortality rate was higher in patients who filled some prescriptions versus those who filled all of their prescriptions: odds ratio, 1.44 and none versus all, odds ratio 1.80.
To improve primary adherence, the researchers urge discharge medication counseling and postdischarge follow-up.

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