It may be possible to use a drug to prevent some of the lasting and crippling damage caused by a stroke, according to doctors in the US and Canada. A safety trial, published in the Lancet Neurology medical journal, suggested the chemical NA-1 was safe to use. The study on 185 people also hinted that patients given the drug developed fewer regions of damaged brain tissue. The Stroke Association said that it was promising, but needed more research. Tests in primates had suggested NA-1 prevented brain cells dying when a stroke starved them of oxygen.