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National HIV/AIDS Program

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Clinical Trials

What are the 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 you 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 your life while you are taking the medicine
is the last phase of study before a drug is sent to the FDA
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 (or doses) of the medicine


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Contents

Clinical Trials

What is a clinical trial?

How do they work?

How do I begin?

What is informed consent?

Does it cost anything?

How long do they last?

Are there different types?

How long before a drug is approved?

Who pays for trials?

What are the benefits and risks?

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Reviewed/Updated Date: September 4, 2008