Actilyse is the brand name of a medicine called tissue plasminogen activator. Its purpose is to make the blood thinner. It is given in acute cases of heart attacks and ischaemic stroke (when the blood supply to the brain is insufficient). However, it must never be given in cases of haemorrhagic stroke (i.e. when the blood supply to the brain is impaired due to bleeding since the drug will make the matter worse). The medicine is given within 6 hours of heart attack or ischaemic stroke. If given inappropriately, it can lead to bleeding. One of its known side effects is bleeding in the brain. It can be given to elderly patients, if required. However, it must not be given to patients with uncontrollably high blood pressure.