Is it safe to take medicines that are still being tested?

Medicines and research: the complex procedure behind it

Almost half of all adults regularly take a prescription medicine 1. If your doctor gives you a prescription, it is very likely that the same type of medicine has been taken before by hundreds, or usually thousands, of other people with the same condition as you. Your doctor will be able to tell you how the medicine is expected to work, and what side effects are most often experienced by people who take it.

This information is available because it has been collected in clinical research studies in which volunteers have taken the medicine while being carefully monitored by doctors. Medicines that are taken as part of clinical research studies (which are also known as ‘experimental’ or ‘investigational’ medicines) are less well understood than most of those prescribed, because there are still questions that need to be answered about their safety and how they work.

How is patient safety ensured in research studies?

Government health authorities – the European Medicines Agency in Europe or the Food and Drug Administration in the USA – are responsible for approving medicines to be used in clinical research studies2. Before a research medicine can be taken by people, the health authority looks for evidence that the risk of serious side effects is low and that there is a good chance the new medicine will have benefits. This may include evidence that shows the medicine can be given to animals without serious harmful effects. The first people to take a research medicine are usually healthy volunteers who are given a very small amount of the medicine. The dose is increased very slowly and carefully. As more and more is learnt about the medicine and how it works, larger studies with more people may begin. At each stage of research, the development of the new medicine will be stopped if serious safety problems are found.2

If a research medicine has a high chance of causing harmful side effects, this will almost always be detected the very first time it is given to humans. Of 17,000 early (Phase I) research studies completed in the past 10 years, very few have reported serious problems 3,4. However, in 2006, six young men in this early stage of research experienced life-changing side effects because of taking an investigational medicine5. As a result, the health authorities made strict new rules to ensure such problems were very unlikely to happen again, such as increasing the amount of information that must be known about the medicine before it is given to humans at the dose thought to be needed for treating a disease6,7.

People taking part in clinical research studies are protected by strict laws, and their well-being is the highest priority for study doctors and nurses. By taking part in a research study, you may be able to benefit from early access to medicines that aren’t yet available outside a study.

How is the safety of a medicine tested before it is given to humans?

Studies of a medicine before it is given to humans are called ‘pre-clinical’ or basic research. Much of this research is either done using animal cells in a laboratory, or by giving the potential new medicine to an animal. Animal studies are carefully controlled and only done when needed; scientists are working to reduce the need for animal testing without increasing the risks to people in clinical research studies8.

Another way to research the activity of medicines in humans is called ‘microdosing’2. This involves giving healthy human volunteers very small amounts of the medicine (much less than would be given to treat a disease). This very low dose is unlikely to pose a serious risk to the volunteer, but may be helpful to scientists who can track the medicine as it moves around the body (it is labelled with a marker that can be seen on a scan). Computers are also playing an increasingly important role in the research of new medicines9,10. Using information about the chemical structure of a medicine, computers can predict how it will be taken into the body and how it interacts with living cells. Currently, computer models are limited by our understanding of diseases – as we learn more, predictions will become more accurate. These research methods may improve the safety of early clinical research studies, and reduce the need for some animal testing.

What are the risks and benefits of taking part in research?

Every year hundreds of thousands of people take part in clinical research studies, and serious side effects are rare. Considering whether to take part in research involves weighing up the possible benefits versus the known and unknown risks11. The risk of taking medicines as part of a research study may be higher than taking a prescribed medicine, although a lot is already known about the research medicine before it is given to people.

People taking part in clinical research studies are protected by strict laws, and their well-being is the highest priority for study doctors and nurses. By taking part in a research study, you may be able to benefit from early access to medicines that aren’t yet available outside a study. You will also be making an important contribution to medical knowledge, which could improve the treatments people receive in future.


  1. Almost half of all adults take prescription drugs. NHS, 2014 Available from: (Accessed October 2016)
  2. The FDA’s Drug Review Process: Ensuring Drugs Are Safe and Effective. The United States Food and Drug Administration. Available from: (Accessed October 2016)
  3. A search for all completed Phase I studies registered on since 1 January 2006 returned 17396 entries (Accessed 28 October 2016).
  4. Emanuel EJ, Bedarida G, Macci K, et al. Quantifying the risks of non-oncology phase I research in healthy volunteers: meta-analysis of phase I studies. BMJ 2015;350:h3271
  5. Northwick Park drug trial disaster could it happen again? BBC Health, 2016 Available from: (Accessed October 2016)
  6. European Medicines Agency 2008, ICH Topic M 3 (R2) Non-Clinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorization for Pharmaceuticals.
  7. Milton MN, Horvath CJ. The EMEA Guideline on First-in-Human Clinical Trials and Its Impact on Pharmaceutical Development. Toxicologic Pathology 2009; 37:363-371.
  8. European Union 2010, Protection of animals used for scientific purposes. EU Directive 2010/63/EU
  9. Virtual Drug Tests, Bayer Pharmaceuticals Available from: (Accessed October 2016)
  10. Lounkine E, Keiser MJ, Whitebread S, et al. Large-scale prediction and testing of drug activity on side-effect targets Nature 2012; 486, 361–367.
  11. Advantages & drawbacks of taking part in a clinical trial. Cancer Research UK, 2015. Available from: (Accessed October 2016)

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