Institutional Review Board for Health Sciences Research (IRB-HSR)

Special Issues

Placebo Controlled Studies


The use of a placebo in clinical research continues to be a topic of debate in the medical community. Some argue that use of placebos is often unethical because alternative study designs would produce similar results with less risk to individual research participants. Others argue that the use of placebos is essential to the protect society from the harm that could result from the widespread use of ineffective medical treatments.

Per the OHRP guidebook, "Placebos may be used in clinical trials where there is no known or available (i.e., FDA-approved) alternative therapy that can be tolerated by subjects." The use of placebos in controlled clinical trials must be justified by a positive risk-benefit analysis, and subjects must be fully informed of the risks involved in assignment to the placebo group. Continued assignment of subjects to placebo is unethical once there is good evidence to support the efficacy of the trial therapy. Some drug trials involve a period during which all participants receive only a placebo prior to the initiation of the study. This period is called a placebo washout. The purposes of a washout period include:

In some protocols, the investigators plan to exclude those subjects they find either poorly compliant or highly responsive to the placebo. The risks entailed in withdrawing subjects from therapy during a placebo washout period will be carefully evaluated by the IRB; great care must be taken to exclude subjects who are vulnerable to harm or injury if they are withdrawn from effective therapy. In studies involving a placebo washout, subjects must be told that at some point during the study all subjects will receive placebo treatment (OHRP Guidebook).

Protocol and Consent Suggestions for Use of Placebo

Researchers should include the following information in the protocol:

The following are methods that can be used to minimize risks associated with the use of placebo:

If a placebo is used in a study, the informed consent form should include all of the following information:

Protocol and Consent Form Suggestions for Placebo Washout Periods

Studies that involve washout periods (with or without the use of a placebo) present similar concerns about risk to subjects as studies using placebos because both involve withholding available therapy from subjects. Therefore, similar attention should be paid to justification of the use of a washout period including methods to minimize risks to subjects. Researchers should include the following information in the protocol:

Algorithm of IRB Evaluation of Studies Involving Placebo

The decision algorithm below will help researchers and IRBs evaluate the ethics of using a placebo-control arm in a clinical research trial.

IRB Evaluation of Studies that Involve Placebo