Sometimes when I write posts I do not stop to think if everyone understands
all of the terms I use. It recently came to my attention that not everyone understands all the terminology used about clinical trials. I thought that I would define the most common terms used.

    Preclinical or Laboratory Studies

These studies are used to determine if the potential drug has any level of effectiveness and if it is safe. These studies are performed on animals.

    Phase I

Simply, the sole purpose of these studies is to determine if the drug is safe and at what dosages can be safely administered. Included in the research is an attempt to establish the best method of administering the treatment and what are the acceptable side effects. These studies are performed on humans, usually from 15 to 50 subjects. All subjects are carefully monitored. The usual subject in a phase I study is a person who no longer has many alternative treatment options available. Placebos have no place in a phase I study.

    Phase II

Phase II studies are used to determine if a drug is effective, or does it accomplish what it goals and have an affect on the disease. Phase II trials tend to have more participants, often 30 to 100 people. Phase II studies will also show additional side effects that might not have surfaced in the Phase I trial. As in a phase I trial placebos are not used.

    Phase III

The phase III study compares the new investigational treatment against the current standard of care treatment. The main question that needs to be answered is if the new treatment modality is better meaning more effective then the current standard treatment. These studies must be robust in the number of subjects participating, often having hundreds or even thousands of subjects. Phase III trials need to have a group of subjects who receive only a placebo.

    Phase IV

In the popular press we rarely hear about a phase IV study. These studies occur after the FDA has approved the treatment. They more carefully examine side effects and hope to follow the eventual outcomes on a longitudinal basis.

Joel T Nowak MA, MSW