Half of Atrial Fibrillation Patients Discontinue Warfarin

More than half of atrial fibrillation patients discontinue or interrupt warfarin therapy within 1 year of starting treatment.

In light of this high prevalence of warfarin discontinuation and interruption, pharmacists should take a more active role in understanding and addressing the underlying causes, researchers from the University of Tennessee College of Pharmacy wrote in the Journal of Managed Care & Specialty Pharmacy.

To measure rates of warfarin discontinuation and interruption in patients with nonvalvular atrial fibrillation (NVAF), and also identify predictors, the researchers retrospectively examined nearly 60,000 adult patients who started warfarin therapy within 30 days of NVAF diagnosis.

All patients were required to be continuously enrolled in prescription drug plans from 6 months prior to warfarin use until at least 1 year after its initiation.

In the study, interruption was defined as a gap in warfarin therapy ≥45 days and ≤90 days between the end date of the former prescription and the start date of the current prescription and without international normalized ratio (INR) monitoring at least every 42 days, while discontinuation was defined as more than 90 days without warfarin therapy between the end date of the former prescription and the start date of the current prescription and without INR monitoring at least every 42 days.

Persistence was defined as warfarin therapy without a gap ≥45 days between the end date of the former prescription and the start date of the current prescription or with INR monitoring at least every 42 days.

Within a year after treatment initiation, 55% of NVAF patients had discontinued or interrupted their warfarin therapy (43% discontinuation, 12% interruption). Less than half (45%) were persistent in their warfarin use.

These results align with several prior studies in the United States. One in particular found that 42.6% of atrial fibrillation patients discontinued warfarin with a gap of at least 90 days between prescriptions within the first year of use, while another found that 51% of NVAF patients discontinued the therapy with a gap over 60 days between prescriptions at least once within a mean follow-up of about 2 years.

In the current study, risk of warfarin discontinuation or interruption was significantly higher among patients who were younger than 65; lived in the western United States; or had anemia, bleeding episodes, or emergency room visits.

On the other hand, those who were female; lived in the north central United States; or had congestive heart failure, hypertension, diabetes, or a history of stroke or transient ischemic attack (TIA) were at significantly lower risk of discontinuing or interrupting warfarin therapy.

“Considering the prevalence of warfarin discontinuation/interruption and the possible consequences for patient health, health care providers should…counsel patients on the risks and costs of discontinuation/ interruption and help patients identify and resolve barriers to consistent use of warfarin,” the study authors concluded. “Health care providers may also want to consider prescribing alternatives anticoagulants, such as newer anticoagulants with more favorable risk benefit profiles and without a need to monitor INR.”