Clot Busters Safe for Warfarin Patients

Warfarin users can safely receive tPA following stroke

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) After a stroke, tPA (tissue plasminogen activator), also known as a clot buster, offers the most effective acute treatment.

However, some patients taking blood thinner Coumadin (warfarin) have not been receiving the drug.

Though doctors are often gun shy about giving clot-busters to patients using warfarin because of a higher risk of potentially fatal bleeding in the brain, the medication can safely be used in the population, a new study found.

"Ask the pharmacist about risks associated with warfarin."

Ying Xian, MD, PhD, assistant professor of medicine at Duke Clinical Research Institute and first author of the study, said there previously were no large studies to offer guidance.

The large national study determined tPA can safely be given to warfarin patients that meet a standard value for the rate at which their blood clots while taking anticoagulants.

In order for the drug to be given safely in warfarin patients after a stroke, the International Normalized Ratio (INR, a measure of how quickly the blood clots) should be less than or equal to 1.7.

It should be noted that an INR of 1.7 would be subtherapeutic for patients with atrial fibrillation.

INR in healthy patients is usually between 0.8 and 1.2, while in patients who need their blood to be thinned, doctors may aim for a 'therapeutic range' of 2.0 to 3.0, indicating that the blood clots slower and the blood is "thinner". 

During the observational trial researchers followed 23,437 stroke patients taking warfarin at more than 1,200 hospitals. Treatments offered to the patients included tPA.

While patients taking warfarin appeared slightly more likely to suffer intracranial bleeding -- 6 percent versus 5 percent -- patients taking the medication also tended to be older. After adjustments for age, stroke severity and other factors, the risk of brain bleeding was found to be similar among both groups.

Researchers also found that about half of patients taking warfarin who suffered a stroke may have qualified to take clot busters, but did not receive the treatment. Dr. Xian said the finding suggested that a portion of the population taking warfarin is being under-treated.

Investigators next plan to examine whether warfarin patients could still benefit from tPA if the speed in which their blood clots is not ideal for the treatment. Additionally they plan to study whether patients taking other newer anticoagulants can safely receive clot busters.

The study was recently published in the Journal of the American Medical Association.

Reviewed by: 
Review Date: 
June 27, 2012
Last Updated:
July 5, 2012