Human clinical trials for treatments undergo four separate stages. The trial may be stopped at the end of any stage. Investigators test its effectiveness and continue to monitor the treatment's safety. During this phase researchers compare it to standard medical procedures and confirm effectiveness, safety, and side effects of the new treatment. Phase IV studies are done after the treatment has been marketed.
Researchers continue to monitor side effects and treatment results in different groups of people.
Due to strict patient guidelines, clinical trials in the past often excluded elderly and minority patients. Elderly patients often have other medical conditions which could influence results. Minority patients may be distrustful of physicians or unable to afford or get to trials. But researchers say it's important to include more diverse populations in studies. Sometimes drugs work differently in various ethnic groups.