Clinical trials at a glance

February 29, 2000
Web posted at: 10:55 a.m. EST (1555 GMT)

In Phase I studies, 20 to 80 people test a new treatment simply to see if it's safe in humans.

In Phase II, 100-300 patients take experimental treatments to test safety further and seek the first hints of whether it works.

Phase III studies enroll several thousand patients to confirm effectiveness and monitor side effects.

In Phase III studies, and sometimes Phase II, patients are randomly assigned to either the experimental treatment, a placebo or standard care. That's how doctors compare whether the new treatment actually works.

Studies also may be "double blind," meaning neither the patient nor the doctor knows who is getting the treatment vs. the comparison until the study ends.

All clinical trials have rules about who can participate, such as age, type of disease, symptoms and medical history.

Healthy people can participate. They often make up Phase I safety trials, and they test vaccines or preventive care.

Patients have the right to quit a trial at any time, but staying until the end is crucial for doctors to prove a treatment's true effects.

Researchers often pay healthy people in Phase I studies. They may reimburse patients for transportation or child care to participate in other studies. But sick people cannot otherwise be paid. The experimental treatment is provided free, but some trials may incur other expenses, something patients should ask.

Copyright 2000   The Associated Press. All rights reserved.