In a Phase III study, a drug is tested in several hundred to several thousand patients. This large scale testing provides the pharmaceutical company and regulatory authorities with a more thorough understanding of the drug's effectiveness, benefits and the range of possible adverse reactions. Most Phase III studies are randomised and blinded trials. Phase III studies typically last several years. Once a Phase III study is successfully completed, a pharmaceutical company can request approval from the regulatory authority for marketing the drug.
People participate in medical research for a variety of reasons.
People who volunteer for Phase II and Phase III trials can gain access to promising drugs long before these compounds are approved for the marketplace. They typically will get excellent care from the doctors during the course of the study. In the UK this treatment will always be free. The ethics committee which is usually composed of doctors and lay people, examines the study's protocol to ensure that patient' rights are protected and that the study does not present an undue risk to the patient. The patient and their carer are required to sign an 'informed consent' form The form details the nature of the study, the risks involved, and what may happen to a patient in the study.