June 27, 2012

Clot-Busting Medicine Ruled Safe for Some Stroke Patients

(Ivanhoe Newswire) — Researchers from the Duke Clinical Research Institute have ruled the clot-busting drug tPA (tissue plasminogen activator) safe for acute stroke patients on the home blood thinner warfarin. The drug was previously thought to be too dangerous to use in patients on home anticoagulation for fear of a higher risk of fatal intracranial bleeding.

"To date, we have no randomized trials or large cohort studies to guide us," Ying Xian, M.D., Ph.D., assistant professor of medicine at Duke, and first author of the study published in JAMA, was quoted as saying. "Our large national study found no statistically significant increase in risk, which supports using intravenous tPA in warfarin-treated patients following stoke if their INR is less than or equal to 1.7."

The International Normalized Ratio (INR) measures the rate at which blood clots while taking anti-clotting drugs like warfarin.

Warfarin is an anticoagulant proven to reduce the rate of stroke in patients with atrial fibrillation (irregular heartbeats). If Warfarin fails to treat the patient and a stroke occurs, tPA is the only effective treatment. Unfortunately, it also carries an increased risk of symptomatic intracranial hemorrhage (sICH).

The American Heart Association guidelines say IV tPA in warfarin-treated patients may be used if the INR is less than or equal to 1.7, but few small studies supported the guidelines.

The observational trial included 23,347 stroke patients taking warfarin treated at 1,203 hospitals; this makes it the largest study to look at IV tPA use in warfarin-treated patients following stroke. Though warfarin-treated patients had slightly higher crude rates of intracranial bleeding than non-warfarin patients (5.7% vs. 4.6%, respectively), they were also older. After the researchers adjusted for age, stroke severity and other factors, warfarin and non-warfarin users had similar risk for intracranial hemorrhage.

"This study provides support for the current treatment guidelines," Xian was quoted as saying, and indicates that a portion of the population is being under-treated.

These findings leave several unanswered questions.  Xian was quoted as saying, "More studies are needed to look at tPA use in patients with an INR greater than 1.7, as well as in those who are taking one of the newer warfarin alternative anticoagulants (dabigatran and rivaroxiban)."

Source: JAMA, June 2012