for Veterans and the Public
Are there different types of clinical trials?
There are four different types of clinical trials: Phase I, Phase II, Phase III, and Phase IV.
Phase I
- is the first time they have tried the drug in people
- tests for the drug's safety and helps find the right dose
- may ask for frequent tests or a stay in the hospital to check for safety and effectiveness
- lasts a fairly short time
- has a small number of patient volunteers
Phase II
- happens when early studies show that the drug may work well to fight HIV
- tests for safety and effective dose level
- lasts longer than Phase I trials
- tries to find out what kind of side effects people may get with this medicine
- has several hundred patients
Phase III
- happens if the drug worked well in Phase I and II
- compares standard treatments (medicines that you can already get by prescription) or sugar pills (placebos) with the new medicine
- may last longer than Phases I and II
- looks for ways to reduce the side effects and improve the quality of life while taking the medicine
- is the last phase of study before a drug is sent to the FDA for consideration for approval
- has many patients (sometimes thousands)
Phase IV
- happens when the drug is already available by prescription
- happens less often than other phases
- checks other safety issues and long-term side effects
- may be used to check higher or lower amounts (doses) of the medicine
See all Clinical Trials
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