There are essential phases required to successfully and safely complete a clinical trial. Clinical trials are most often only conducted once a potential new treatment is approaching readiness for the open market. It is not safe to send new medication to the public market without proper safety and efficacy testing. 

It is also not safe to randomly test new medications on humans without knowing the risks and potential outcomes first. The phases of a clinical trial are designed to mitigate risks while also yielding the most accurate results possible.

Phases of a Clinical Trial

Once a potential new treatment/medication successfully migrates from laboratory animal-based testing trials, clinical trials using human participants begin. There are five phases to clinical trials using human participants. A Phase 0 clinical trial studies the way a potential new medicine is absorbed by, and processed through the human biological system.

Phase 0 facilitators administer small doses of the medicine being tested to approximately ten to fifteen participants. Once Phase 0 is complete, Phases 1 through 4 then push the experimentation and studies further.

A Phase 1 clinical trial has the primary goal of determining the best dosage of a potential new medication with also the fewest side effects. The participant pool is expanded to fifteen to thirty people and dosages are increased in only some of the participants. A Phase 2 clinical trial further assesses the safety of the potential new medication. Larger groups of participants are used. 

New combinations of the medication(s) are also employed. A Phase 3 clinical trial compares the potential new medication with the standard medication currently on the market. Side effects of the new and the standard medications are compared. Participant groups are expanded to one hundred people. 

More than one participant group might be used. Phase 3 also often uses randomization via computer systems to ensure accuracy. Finally, the Phase 4 clinical trial is activated in order to test potential new drugs approved by the U.S. Food and Drug Administration (FDA). 

Participant groups are expanded to hundreds or thousands of people. Short-term and long-term side effects are tested more extensively. A Phase 4 clinical trial is the last step before a potential new treatment/medication is released on the open market.