Discovery and development of drugs

New medical drugs must be tested and trialled before being used to check that they are safe and effective. 

1. New drugs are extensively tested in the laboratory for toxicity, efficacy (how well it works) and dose. This will include using computer models to understand how the drug might affect human cells and proteins.

2. Preclinical testing is done in a laboratory using cells, tissues and live animals. The drugs are not tested on humans at this stage. Scientists will look for the response they are expecting, and also for any potential toxicity or side effects.

3. Clinical trials, using healthy volunteers and patients, start with very low doses of the drug on a small number of volunteers to check for safety. 

4. If the drug is found to be safe, further clinical trials are carried out using more volunteers to find the optimum dose for the drug. 

Many clinical trials are double-blind trials, which means that some patients are given a placebo while others are given the real drug. A placebo is something that looks the same as the real drug and has all the same ingredients except it contains none of the drug. This allows scientists to see if it is the drug that causes the effect. Only the scientists who analyse the results know who receives which, so neither the patient nor the doctors know which is the placebo and which is the drug. This prevents any bias in the study.

The results of testing and trials are published only after scrutiny by peer review. This means the results are carefully checked by other specialist scientists who can check if the conclusions are correct. This is because drugs need to be safe and effective before they can be used more extensively.