ABSTRACT
When designing a study to show that an experimental therapy is effective, it is sometimes possible to include a third arm in the study to obtain data on both a concurrent placebo control and an active control. Earlier in this book, we considered two-arm non-inferiority trials having only an active control when the use of a placebo control is unethical or problematic-for example, if an effective treatment is available for a disease with obvious discomfort or irreversible morbidity, it may be difcult to obtain permission from an ethical review board to include a placebo control and most likely impossible to obtain informed consent from potential study subjects. Alternatively, when a placebo control is ethical, the comparison of an experimental treatment to a placebo control is the gold standard and inclusion of an active control is generally not required. However, there are situations in which inclusion of both a placebo control and an active control are ethically and scientically defensible.
