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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