Enoxaparin is more effective than unfractionated heparin for prevention of venous thromboembolism after acute ischemic stroke, according to a presentation at the annual meeting of the American Society of Hematology.

Acute ischemic stroke is one of the vascular events associated with increased risk for venous thromboembolism: Without prophylaxis, up to 75 percent of patients with hemiplegia associated with acute stroke develop deep vein thrombosis. Up to 20 percent have a pulmonary embolism.

The PREVAIL trial was the first large-scale, multinational, prospective, randomized study to examine prophylaxis in this population, enrolling 1,762 patients stratified by NIH Stroke Scale Score in over 15 countries.

After confirmation of acute ischemic stroke, patients were randomized within 48 hours of stroke symptoms to receive enoxaparin 40 mg subcutaneously daily 40 or unfractionated heparin 5000 Units every 12 hours subcutaneously for roughly 10 days; follow up was 90 days, and data were stratified by NIH Stroke Scale Score (severe greater than or equal to 14 and less severe less than14).

The primary efficacy endpoint was the composite of symptomatic or asymptomatic deep vein thrombosis and symptomatic and or fatal pulmonary embolism during treatment. Primary safety endpoints included symptomatic intracranial bleeding, major extracranial bleeding and all-cause mortality.

Enoxaparin was associated with a significant 43 percent relative risk reduction in thromboembolic events compared with unfractionated heparin. There was no significant difference in clinically important bleeds (1.3 percent versus 0.7 percent).
"Balancing the benefits of lowering the risk of venous thromboembolism while minimizing the risk of bleeding is a very important element in choosing prophylactic regimens for this particularly fragile patient population, as it combines the usual factors of venous thromboembolism in addition to the stroke context," said David Sherman, MD, the principal investigator of the study. "PREVAIL showed that enoxaparin, when compared to unfractionated heparin, had a superior efficacy with no significant increase in clinically important bleedings. These data provide new evidence that suggests enoxaparin can be used as venous thromboembolism prophylaxis in this high risk population".