Researchers at Edinburgh University have conducted the largest ever clinical trial of the drug rt-PA and have discovered major benefits for more stroke victims. Rt-PA is currently administered intravenously to patients under the age of 80 who have suffered an acute ischemic stroke and within four and a half hours of this occurring.  An ‘ischemic stroke’ occurs after the blood supply to the brain has been decreased and this can happen due to a number of reasons such as embolism, thrombosis, systemic hypoperfusion and venous thrombosis. The victim can be left paralysed, with speech problems and sometimes the stroke can be more fatal. An ischemic stroke can be treated in a hospital with thrombolysis, which is also sometimes known as a ‘clot buster’. The new study involved over 3,000 patients, where over half were over the age of 80 years old. It was found that there was no increase in deaths at six months and survivors had less disability as a result of their stroke. Professor Richard Lindley of the Edinburgh University, initially created the trial back in 2000, and has continued to be actively involved in it. He commented on some of the findings, "The trial underlines the benefits of treating patients with the drug as soon as possible and provides the first reliable evidence that treatment is effective for those aged 80 and over," Professor Lindley said. Professor Lindley also noted that the current four and a half hour time window for administering rt-PA was still appropriate but that treatment up to six hours could be beneficial in selected patients. Researchers have however warned that there are elements of risk involved with taking rt-PA. Within the first week of treatment, the medication does pose a threat of inducing a secondary bleed in the brain. Even with these risks, the trials showed that a wide range of patients benefited from the drug. In addition, the chance of the patients making a full recovery after six months was also greatly increased. In 1,000 of the patients, if they were administered the drug within a three hour time frame, their chances of survival increased yet again.