What are Clinical Trials?
Clinical trials show the benefits and risks of healthcare interventions - such as medicines, surgery or radiotherapy - by comparing them with the standard treatments currently in use or with a dummy drug or ‘placebo’. The treatments are given to patients and/or healthy people, and the researchers then observe and record any differences in their effects over time.
Most clinical trials are randomised controlled trials. These are designed to compare two or more treatments as fairly as possible, by allocating the different treatments to participants on a random basis to reduce the likelihood of bias.
Clinical trials can also show that an existing treatment isn’t the best one to use. For example, earlier this decade, an MRC-funded trial showed that routine corticosteroid treatment for head injury patients does more harm than good.
Types of clinical trials
- Treatment trials, designed to assess ways of treating specific health conditions, are the most common type of clinical trials. Many of these trials test drugs or combinations of drugs. Others test procedures such as surgery, or medical technology and devices, or educational interventions.
- Prevention trials test ways to prevent specific health conditions. Drugs, vitamins, education, life style changes, or other interventions may be tested.
- Screening trials test ways to detect and diagnose health conditions and diseases.
Stages of a clinical trial:
Phase I: this stage involves a small number of participants – usually healthy – to evaluate how a new drug should be given, how often and at what dose.
Phase II: the researchers continue to test the safety and acceptability of the drug, and begin to assess whether it works on people with the condition it is designed to treat.
Phase III: at this trial stage a new drug or a new combination of drugs is compared with the current standard treatment. Participants are assigned to a standard treatment or the new treatment on a random basis. This reduces bias, so that the researchers can be confident that the trial results reveal the differences between the treatments rather than differences between the people receiving them. Phase III trials often involve large numbers of volunteers and may be conducted at doctors’ surgeries, hospitals and centres throughout the country. Most of the trials we fund are phase III trials.
Phase IV: This trial phase tests the long-term effects of a treatment, sometimes after it has been introduced into everyday clinical practice.