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Managing Overprescription of Oral Anticoagulants


December 06, 2016

Jonathan Hsu, MD, MAS, an assistant professor at the University of California, San Diego, has led research that identified gaps in the care of atrial fibrillation (AF) patients. One of his studies highlighted a widespread misconception that antiplatelet therapy alone matches anticoagulation in protecting at-risk AF patients from stroke. Another study he headlined examined the records of nearly 11,000 AF patients younger than 60 years with no structural heart disease and low risk for thromboembolism. Approximately 2,500 patients in the study who were prescribed oral anticoagulants shouldn’t have received the therapy according to current treatment recommendations. The findings highlighted the potential inappropriate prescription of oral anticoagulation in young and healthy AF patients when bleeding risks may outweigh a stroke-reduction benefit.

Dr. Hsu recently shared his insights for improving the use of anticoagulants to treat all AF patients, including those at greatest risk of stroke. He also emphasized the importance of physicians and pharmacists working together to ensure anticoagulants are dosed and prescribed properly.

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What was the main purpose of studying  antiplatelet and anticoagulant prescribing patterns?

Atrial fibrillation is the most common cardiac arrhythmia worldwide and imparts significant stroke risk. For AF patients at intermediate to high risk for thromboembolism, anticoagulation with warfarin or the newer non-vitamin K antagonist oral anticoagulants clearly reduces morbidity and mortality more than aspirin alone. We sought to evaluate practice patterns of cardiovascular specialists in the United States to determine how often AF patients at risk of stroke are prescribed aspirin over oral anticoagulation, and predictors of this practice. We found that approximately 40% of more than 200,000 outpatients with AF who were at intermediate to high risk of stroke were treated with aspirin alone instead of oral anticoagulant prescription.

Were certain patients more likely to receive aspirin instead of anticoagulants?

Yes, specific patient characteristics predicted prescription of aspirin therapy over oral anticoagulation, particularly comorbidities related to coronary atherosclerosis and its risk equivalent diseases — hypertension, dyslipidemia, coronary artery disease, prior myocardial infarction, unstable and stable angina, recent coronary artery bypass grafting, and peripheral arterial disease. The results were somewhat surprising and highlight the need to improve the prescribing of oral anticoagulation in AF patients at risk of stroke, because aspirin therapy alone is often not enough to protect these patients from life-threatening consequences.

Your research has also shown that AF patients at low risk of stroke may be prescribed oral anticoagulants unnecessarily. What did that study reveal?

Those findings were surprising, as we did not expect approximately 1 in 4 AF patients to be prescribed oral anticoagulation, despite being at the lowest risk of stroke. It was a wake-up call. Physicians and pharmacists should be aware that the decision to start anticoagulation in AF patients hinges upon clinical risk factors associated with stroke. Without any risk factors, contemporary guideline recommendations suggest withholding oral anticoagulation therapy.

What are the underlying causes of gaps in care of AF patients?

The reasons for subpar guideline adherence to oral anticoagulation in AF patients are likely multifactorial. Prescribers may underestimate the yearly stroke risk of patients with AF, and overestimate the bleeding risk of prescribing oral anticoagulation. These miscalculations, along with misperceptions about the therapy, may cause physicians to avoid prescribing oral anticoagulants when they’re indicated. Certainly, cardiology specialists should be aware that patients at significant stroke need potentially life-saving medications. However, there is likely a component of both patient and practitioner reluctance to prescribe anticoagulants due to fear of bleeding, which is often unfounded. It will take concerted efforts to educate practitioners and patients about the benefits of anti-clotting medications to improve oral anticoagulation practices.

What can health-system pharmacists do to ensure the proper and effective use of anticoagulants?
Pharmacists have expanded roles in ensuring the effective use of oral anticoagulants. Their involvement in warfarin clinics has been shown to improve patient outcomes. They also help to ensure the effective and appropriate prescribing of new oral anticoagulants, as dosing based on renal function is imperative. Having a medical professional who is expert in these subtleties will be essential in improving the proper prescribing of these newer medications. Prescribing physicians appreciate active involvement by pharmacists and they’re always grateful when an astute pharmacist catches a drug-drug interaction or the renal dosing change of a medication. Ultimately, prescribers and pharmacists must team up in order to enhance the care of AF patients.

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Sources

1. Aspirin Instead of Oral Anticoagulant Prescription in Atrial Fibrillation Patients at Risk for Stroke. Journal of the American College of Cardiology. http://bit.ly/28KpSMH

2. Oral Anticoagulant Prescription in Patients With Atrial Fibrillation and a Low Risk of Thromboembolism: Insights From the NCDR PINNACLE Registry JAMA Internal Medicine. http://bit.ly/2gQI4p6.

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