In a clinical trial, participants receive specific interventions according to the research plan or protocol created by the investigators. These interventions may be medical products, such as drugs or devices; procedures; or changes to participants' behavior, such as diet. Clinical trials may compare a new medical approach to a standard one that is already available, to a placebo that contains no active ingredients, or to no intervention. Some clinical trials compare interventions that are already available to each other. When a new product or approach is being studied, it is not usually known whether it will be helpful, harmful, or no different than available alternatives (including no intervention). The investigators give patients investigational medicines and then measure certain outcomes in the participants, which is used to learn more about the safety and efficacy of the investigational medicine.
Clinical trials used in drug development are sometimes described by phase. These phases are defined by the regulatory agencies.
*National Library of Medicine (NLM) and ClinicalTrials.gov. (2019, March) Learn About Clinical Studies. Retrieved October 3, 2019, from http://www.clinicaltrials.gov/.