Phase I tests safety, providing humans with the first exposure to the treatment. Phase II monitors safety and side effects and determines effective dosing. In Phase III, the drug is studied in protocols with large numbers of patients to judge its relative safety and effectiveness. New drug testing is the most common type of clinical trial. Prevention studies look at medicines or lifestyle changes that may help prevent disease.
Diagnostic studies address ways of detecting or learning more about a disease.
In treatment studies, new drugs or new combinations of established treatments are monitored. No matter what type of trial you're in, an informed consent trial is mandatory. By signing the form, you acknowledge that you understand the purpose of the study, the time involved, potential risks and benefits and whether compensation is included. Your signature does not, however, stop you from dropping out of the study at any time. Once you get started, the process of informed consent should continue throughout the trial.