Trial Design
Placebo
A placebo is an inactive substance or sham intervention designed to be indistinguishable from the active investigational treatment, used as a control to isolate the specific effect of the intervention from non-specific effects.
Placebo controls are most defensible when no proven effective therapy exists, when adding placebo to standard care is ethical, or when a short placebo run-in does not expose patients to undue risk. The Declaration of Helsinki and ICH E10 set ethical limits on placebo use.
In some indications (oncology, severe infection) placebo controls are replaced by active comparators; non-inferiority designs are used to show the new therapy is not meaningfully worse than the standard of care.
Related terms
Blinding (Masking)
Blinding (also called masking) is the practice of withholding information about treatment assignment from one or more parties in a clinical trial to prevent bias in outcome assessment, behavior, and analysis.
Randomization
Randomization is the process of assigning clinical trial participants to treatment groups by chance, eliminating selection bias and producing comparable groups for unbiased estimation of treatment effects.
Intention-to-Treat (ITT) Analysis
Intention-to-treat (ITT) analysis is a statistical principle requiring that all randomized participants be analyzed in the treatment group to which they were originally assigned, regardless of whether they completed, switched, or never received the assigned treatment.
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