Clinical trials are conducted in phases. The trials at each phase have a different purpose and help scientists answer different questions:
• Phase I Trials – In Phase I trials, researchers test an investigational drug or treatment in a small group of people (20-80) to evaluate its safety, determine a safe dosage range, and identify any side effects. Many times Phase I trials are conducted using only healthy volunteers. Phase I trials are the first time an investigational treatment is tested on humans; however, substantive research with and testing of the investigational medication has already occurred, with favourable results, to get to this stage of the process.
• Phase II Trials – In Phase II trials, the investigational drug or treatment is given to a larger group of people (100-300) with the targeted medical condition to see if it is effective and to further evaluate its safety.
• Phase III Trials – In Phase III trials, the investigational drug or treatment is given to large groups of people (1,000-3,000) with the targeted medical condition to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the investigational treatment to be used safely.
• Phase IV Trials – In Phase IV trials, additional information, including the drug’s risks, benefits, and optimal use, is collected.