The protocol contains a study plan on which the clinical trial is based. The plan is designed to safeguard the health of the participants (while limiting their financial liability) as well as answer specific research questions. The protocol describes, among other things, what types of people may participate in the trial; the schedule of tests, procedures, medications, and dosages; and the length of the study. While in a clinical trial, study participants are seen regularly by the research staff (usually medical doctors and/or nurses) to monitor their health and to determine the safety and effectiveness of the treatment(s) they are receiving.
The format and content of clinical trial protocols sponsored by pharmaceutical, biotechnology or medical device companies in the United States, European Union, or Japan has been standardized: they are written to follow the Good clinical practice guidance issued by the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) Regulatory authorities in Canada and Australia also follow the ICH guidance.
Clinical trial protocols for other clinical trials do not necessarily follow the standard format.
The existence of a clinical trial protocol allows researchers at multiple locations (in a multicenter trial) to perform the study in exactly the same way, so that their data can be combined as though they were all working together. The protocol also gives the study administrators (often a contract research organization) as well as the local researchers a common reference document for the researchers' duties and responsibilities during the trial.