Question: What is a Placebo?
Frequently you hear about placebos being used in medical drug trials. A placebo is an inert substance sometimes called a "sugar pill" that may be given instead of the drug.
Answer: Scientists often use placebos to study the effects of a new drug. They do this by giving a certain number of trial participants the real drug being tested, and the rest of the participants are given another substance that lacks medical or therapeutic value. The trial participants do not know if they are being given the drug or the placebo. Sometimes the doctors or scientists monitoring the patients and dispensing the drug do not know which one their patient is getting until after the trial is over.
You may have also heard the phrase "the placebo effect." This refers to the idea that if a person is given something -- a drug or other treatment -- that he thinks will help him, his symptoms may improve. This effect is well-known and accounted for when a new drug is being tested. This is why sometimes people in a clinical trial experience improvement in their disease symptoms, even if they are not given the real drug.
Placebo ethics are often under debate. However, in clinical trials, all the participants are aware that they might be given a placebo.
Sources:
U.S. Food and Drug Administration. "Clinical Trials." Office of Women's Health 2005 Aug. 28 Feb 2008.