BEIJING, Feb. 24 -- A study aiming to expand the three-hour time window for giving a clot-busting drug to stroke patients fell short of its goal, according to Australian researchers.

    But the study hinted that certain stroke sufferers might still benefit from late administration of the drug.

    They had hoped to prove the clot-buster known as tissue plasminogen activator or tPA would significantly reduce the spread of a stroke three to six hours after the first symptoms appeared.

    Under present guidelines, the drug can only be given within three hours of the first symptoms, a restriction that leaves out all but a lucky few who get immediate help.

    When given promptly, tPA can reduce permanent disability. It only works on ischemic stroke, which is caused when a blood clot chokes off blood flow to the brain.

    Stephen Davis of Royal Melbourne Hospital in the state of Victoria wanted to see if the drug could help a subset of stroke patients with salvageable brain tissue after the three-hour time limit had passed.

    He and colleagues studied 101 patients who received tPA or placebos three to six hours after their stroke started.

    Of these, 99 people were believed to have salvageable brain tissue. About half of these got tPA and half got placebo.

    While the late use of the drug did not show statistically significant improvement, it did show a strong trend toward saving brain tissue, Davis said on Friday. His study was published in the journal Lancet.

    The drug also helped improve blood flow into the damaged area, a finding that was statistically significant.

    Researchers said the study, known as EPITHET, suggests extending the time window beyond three hours could be useful for some patients.

    "EPITHET provides strong encouragement but it should not change any clinical guidelines," Davis told a media briefing at the American Stroke Association's International Stroke Conference in New Orleans.

    At the same conference, researchers said a device that suctions out blood clots helped improve blood flow to the brain in 82 percent of 125 patients studied, even eight hours after the onset of the stroke.

    About 40 percent of the patients showed improvement 30 days after treatment.

    The study tested the Penumbra System, made by privately held Penumbra Inc. of Leandro, California.    

    (Source: Shanghai Daily/Agencies)