Study DesignGlossary Term
An inactive substance or treatment that is designed to appear identical to the investigational product but contains no therapeutic ingredients.
A placebo serves as a methodological tool in clinical research, providing a control condition against which the effects of an active treatment can be measured. By mimicking the investigational product in appearance, taste, smell, and mode of administration without containing the active therapeutic ingredient, placebos enable researchers to distinguish true drug effects from responses attributable to the treatment experience itself, natural disease progression, or other non-specific factors.
The placebo effect represents a genuine physiological and psychological phenomenon in which participants experience measurable improvements after receiving an inert substance. This effect can be substantial in conditions involving subjective symptoms such as pain, depression, and anxiety, making placebo controls essential for accurate assessment of drug efficacy. Without a placebo comparison, apparent treatment benefits might be incorrectly attributed to pharmacological activity when they actually reflect the natural history of the disease or participant expectations.
The ethical use of placebos in clinical trials requires careful consideration. Placebo controls are generally considered appropriate when no proven effective treatment exists for the condition under study, when withholding treatment poses minimal risk, when compelling methodological reasons necessitate a placebo comparison despite available treatments, or when participants would not be denied access to proven therapy. The Declaration of Helsinki and GCP guidelines require that the use of placebo be scientifically justified and that participants are fully informed about the possibility of receiving placebo during the consent process.
Double-blind trial
"In the Phase III depression study, half of the participants received the investigational antidepressant while the other half received a placebo capsule identical in appearance, with neither group nor the investigators knowing which treatment was administered."
Ethical considerations
"The ethics committee approved the placebo-controlled design for the migraine prevention trial because participants were permitted to use their standard rescue medications for acute attacks, ensuring they were not denied effective treatment."
The fraction of an administered dose of a drug that reaches the systemic circulation unchanged, and the rate at which this occurs.
A group of participants in a clinical trial who receive a comparator treatment, placebo, or no treatment to serve as a baseline for evaluating the effects of the investigational intervention.
A clinical trial design in which participants receive multiple treatments in sequence, with each participant serving as their own control by receiving all study treatments during different periods.
A systematic approach to increasing the dose of an investigational product during a clinical trial, typically employed in early-phase studies to identify safe and potentially effective dose levels.
A clinical trial in which both the participants and the investigators are unaware of the treatment assignments, providing maximal protection against bias in the conduct and assessment of the study.
An inactive substance or treatment that is designed to appear identical to the investigational product but contains no therapeutic ingredients.
A placebo serves as a methodological tool in clinical research, providing a control condition against which the effects of an active treatment can be measured. By mimicking the investigational product in appearance, taste, smell, and mode of administration without containing the active therapeutic ingredient, placebos enable researchers to distinguish true drug effects from responses attributable to the treatment experience itself, natural disease progression, or other non-specific factors.
The placebo effect represents a genuine physiological and psychological phenomenon in which participants experience measurable improvements after receiving an inert substance. This effect can be substantial in conditions involving subjective symptoms such as pain, depression, and anxiety, making placebo controls essential for accurate assessment of drug efficacy. Without a placebo comparison, apparent treatment benefits might be incorrectly attributed to pharmacological activity when they actually reflect the natural history of the disease or participant expectations.
The ethical use of placebos in clinical trials requires careful consideration. Placebo controls are generally considered appropriate when no proven effective treatment exists for the condition under study, when withholding treatment poses minimal risk, when compelling methodological reasons necessitate a placebo comparison despite available treatments, or when participants would not be denied access to proven therapy. The Declaration of Helsinki and GCP guidelines require that the use of placebo be scientifically justified and that participants are fully informed about the possibility of receiving placebo during the consent process.
Double-blind trial
"In the Phase III depression study, half of the participants received the investigational antidepressant while the other half received a placebo capsule identical in appearance, with neither group nor the investigators knowing which treatment was administered."
Ethical considerations
"The ethics committee approved the placebo-controlled design for the migraine prevention trial because participants were permitted to use their standard rescue medications for acute attacks, ensuring they were not denied effective treatment."
The fraction of an administered dose of a drug that reaches the systemic circulation unchanged, and the rate at which this occurs.
A group of participants in a clinical trial who receive a comparator treatment, placebo, or no treatment to serve as a baseline for evaluating the effects of the investigational intervention.
A clinical trial design in which participants receive multiple treatments in sequence, with each participant serving as their own control by receiving all study treatments during different periods.
A systematic approach to increasing the dose of an investigational product during a clinical trial, typically employed in early-phase studies to identify safe and potentially effective dose levels.
A clinical trial in which both the participants and the investigators are unaware of the treatment assignments, providing maximal protection against bias in the conduct and assessment of the study.