Study: Anticoagulant Apixaban Better than Warfarin

Patients with atrial fibrillation have a substantially reduced risk of dangerous bleeding in the brain ("intracranial haemorrhage") when taking the newer anticoagulant apixaban compared to those taking warfarin, according to a new study published in the journal Blood. Researchers also found that taking aspirin increased the risk of intracranial haemorrhage, especially in older patients.

See Also: Warfarin Does Not Offer Long-Term Stability for Atrial Fibrillation

Atrial fibrillation (AFib) is a type of irregular heartbeat that can lead to blood clots, stroke and other heart-related complications. The use of oral anticoagulant medications is recommended for patients with AFib who are at high risk for stroke. These medications reduce the blood's clotting ability, which substantially lowers the risk of stroke, but also increases the risk of uncontrolled bleeding. Intracranial haemorrhage is a rare, but serious complication of these medications, occurring in about one percent of patients prescribed anticoagulants for AFib. This type of bleeding in the brain can occur spontaneously or after trauma (such as a fall).

"This study shows apixaban is a better option for oral anticoagulation than warfarin because it reduces stroke while substantially reducing intracranial haemorrhage," said lead author Renato D. Lopes, MD, PhD, a cardiologist at Duke Clinical Research Institute.

Historically, warfarin, a vitamin-K antagonist, has been considered the standard of care for oral anticoagulation therapy, but warfarin requires careful management to ensure patients receive the proper dosing. Drugs in a class of newer anticoagulants known as non-vitamin K antagonist oral anticoagulants (NOACs) are easier to manage and have been shown to be as effective as warfarin.
 
The study is the first to compare apixaban, a NOAC, to traditional warfarin in terms of the risk for intracranial haemorrhage. Dr. Lopes and colleagues analysed data from the ARISTOTLE trial, which enrolled more than 18,000 patients in North America, Latin America, Europe, and Asia. All patients had AFib and at least one additional risk factor for stroke. Patients were randomised to each medicine; half received apixaban and half received warfarin. Outcomes were tracked for a median of 1.8 years.

Intracranial haemorrhage occurred at a rate of 0.80 percent per year in patients taking warfarin and 0.33 percent per year in patients taking apixaban, meaning that patients taking apixaban were 58 percent less likely to experience intracranial haemorrhage compared to those taking warfarin. The difference was even greater for patients experiencing trauma-related intracranial haemorrhage; patients taking apixaban were 75 percent less likely to experience trauma-related bleeding compared to those taking warfarin. The results were consistent across all types and locations of bleeding in the brain.

Taking concomitant aspirin at the start of the study was found to significantly increase the risk of intracranial haemorrhage, especially in older patients. About 30 percent of patients with AFib use aspirin. Aspirin is a blood thinner that prevents platelets from clumping together, but it is not an anticoagulant medication and is not considered to effectively prevent strokes in AFib patients.

"We know that aspirin has only a modest effect in preventing stroke in atrial fibrillation patients, yet it was one of the top predictors of intracranial haemorrhage," Dr. Lopes noted. "Our finding demonstrates that aspirin is not as safe as one might think."

Source: American Society of Hematology
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