Before a new medicine is available for general use, it will undergo a thorough trial process. This is to see how well it works and to make sure it is safe to use. This trial process usually lasts for several years.

To see how well a medicine works, we look at data from clinical trials. Clinical trials are used to test a medicine to make sure it works and is safe.

The most reliable clinical trials compare what happens in people taking the medicine to what happens to people taking a different medicine. Or to people taking a dummy treatment that looks the same but does not have any medicine in it. This is called a placebo. It lets us see how many people have got better because of the medicine, and how many people might have got better with a different medicine. Or without any medicine at all.

Clinical trials do not always reflect the way medicines are used in real life. They have strict rules on who can and cannot take part. So the people who are involved in clinical trials might not be the same as the people in a general IBD clinic. For example, they might not include people who are pregnant or breastfeeding, have had cancer or have another illness, or are over a certain age. To start with we might not be able to say much about using a particular medicine in these groups of people. They often have strict rules on when treatment needs to be started or stopped. People who have treatment as part of a clinical trial might have appointments and tests more often than you would in real life. All these things could affect the results.

This means that how well a medicine works in a clinical trial might not be the same as how well it works in real life. It could be better or worse. But clinical trials are still the best way that we can understand how well new treatments work and how safe they are.

Once a medicine has been approved, more people will start using it outside of the clinical trials. This is sometimes called real world evidence. This tells us more about how well the medicine works and how safe it is in a wider range of people.

Find out more about how medicines are developed