This information is for people who have an ischaemic stroke. It tells you about clot-dissolving (thrombolytic) drugs, a treatment used for this type of stroke. It is based on the best and most up-to-date research.
Do they work?
Yes. If you get one of these drugs within three hours of the beginning of your stroke symptoms, you are less likely to need nursing care in the future. They may still work if you have them within six hours of your stroke.
But in some people these drugs can be dangerous. They can cause death from bleeding in the brain.
For this reason, doctors have to weigh up the increased likelihood of being alive and independent in the long run against the increased risk of death in the short term.
What are they?
Clot-dissolving drugs are a group of medicines that are often referred to as clot-busters, because they break up or dissolve clots that have formed in a blood vessel. This lets the normal flow of blood restart.
Some common clot-dissolving drugs (and their brand names) are:
Most clot-dissolving drugs do the same thing as a natural chemical in your body called tissue plasminogen activator (t-PA). This chemical stops your blood clotting when it shouldn't. But alteplase is different. It's called a recombinant tissue plasminogen activator (rt-PA).
Alteplase is genetically engineered (made in a laboratory) and is an exact copy of the t-PA found in your body. Scientists are able to match this substance exactly because they've found the gene responsible for making t-PA in the body. They have cloned this gene to make rt-PA outside the body. Human insulin is made the same way.
Clot-dissolving drugs are usually given as a drip (also called an IV or an intravenous infusion).
Only alteplase is licensed to be used in the UK to treat people who have had a stroke. There are strict guidelines for using it.   Alteplase should only be given by a specialist.
You will need to have a brain scan before getting this treatment to make sure you have not had bleeding in your brain (a haemorrhagic stroke).
Your doctor will also ask you or a relative when your symptoms started, as it's best to give this drug within three hours of the start of a stroke. But it can be difficult to be certain about when stroke symptoms began. For example, many people wake up with the symptoms, which could have started at any time during the night.
The National Institute for Health and Clinical Excellence (NICE), which advises the government about health care, says alteplase should be used as an emergency treatment for stroke, as long as all these guidelines have been followed.