London, May 15 (IANS): Patients who receive treatment within 90 minutes of a stroke attack are twice as likely to increase the chances of good recovery, say researchers.

Researchers from University of Glasgow have found that patients given a blood thinning drug to restore blood flow in the brain within 90 minutes of their symptoms were two and half times more likely to have a good recovery than those not given the drug.

Although patients did benefit from the drug, called alteplase, when given later but to a lesser extent.

The analysis of 3,670 patients in eight studies showed that the earlier the drug was given the greater the chance the patient would recover without suffering lasting disabilities.

But even those who received it up to four and half hours after their symptoms started, still showed some benefit and were 22 per cent more likely to have a good recovery than those not given the drug.

The analysis found that patients treated within 90 minutes were 22 percent less likely to die, but the chance of dying increased with the length of time it took for treatment to start.

"Our analysis showed that the greatest benefit comes from earlier treatment, since net benefit is diminishing and is undetectable in our sample beyond 4.5 hours,:" telegraph.co.uk quoted lead author Kennedy Lees, from the University of Glasgow, as saying.

"However, alteplase does not result in excellent benefit in most patients, even those treated early, so questions remain.

"We need to understand better the factors that prevent alteplase from being effective in individual patients.

"Patients with ischemic stroke selected by clinical symptoms and CT benefit from intravenous alteplase when treated up to 4·5 hours. To increase benefit to a maximum, every effort should be taken to shorten delay in initiation of treatment. Beyond 4·5 hours, risk might outweigh benefit," Lees added.

The study appears in journal The Lancet.