Understanding clinical study phases
Clinical studies are classified under four phases:
Researchers test an investigational drug
in a small number of people by giving it to either healthy volunteers or patients to evaluate its safety, determine a safe dosage range and identify side effects.
The investigational drug
is given to a larger number of people who have a particular disease or condition
to further evaluate its safety and often to assess
Several hundred to several thousand people with the appropriate disease or condition
participate in these studies. The investigational drug
undergoes additional testing to further determine its safety and effectiveness, monitor
side effects, and compare it to commonly used treatments or placebo
After a drug is available by prescription
, additional information about a drug's risks, benefits and use may be gathered.