Understanding clinical study phases
Clinical studies are classified under four phases:
Phase l: 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.
Phase ll: 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 its effectiveness.
Phase lll: 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.
Phase lV: After a drug is available by
prescription, additional information about a drug's risks, benefits and use may be gathered.