Clinical Trial Phases Broken Down

Clinical Trial Phases Broken Down



Phase 0

Objective: Analyze how the medication is processed within the body and ensure the safety of human consumption.

Number of Participants: Fewer than 15

Length of Phase: Several months


Phase I

Objective: Determine the ideal consumption frequency and the highest dose of treatment that patients can handle without major or harmful side effects. 

Number of Participants: Fewer than 30

Length of Phase: Up to 1 year


Phase II

Objective: Determine the effectiveness of the drug. In this phase, different combinations of medications are often tested. However, these drugs are rarely compared to current standard-of-care medications. 

Number of Participants: Several hundred

Length of Phase: Up to 2 years


Phase III

Objective: Definitively decide if the new drug performs better than the current standard-of-care drug. Patients are separated into randomized groups to test the new drug against a control group using the current standard-of-care drug. Patients do not know which group they’re in until the trial has been completed in an effort to avoid the placebo effect. 

Number of Participants: Up to 3,000 

Length of Phase: Several years but will be cut short in the event of significant results 


Phase IV

Objective: Discover long-term and/or unique side effects not noticed in immediate phases as well as overall long-term effectiveness. This phase begins after the medication has been approved by the FDA. 

Number of Participants: Several thousand 

Length of Phase: Several years




Q: Why are clinical trials performed?

A: Clinical trials are performed when there is a reason to believe that a new drug may improve a patient’s care. 


Q: Do I need to participate in all phases of the trial? 

A: No, you may participate in any phase that is open to you. 


Q: Why are trials “randomized”? 

A: Doctors use a computer program to randomize clinical trials and ensure the results are unbiased.  


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By |2019-07-31T17:31:00-04:00July 8th, 2019|

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