Placebo-controlled trials and active-control trials in the evaluation of new treatments - Part 2: Practical issues and specific cases

Placebo controls are commonly used in clinical trials of investigational tr eatments because they have important advantages. In recent years, some have criticized the use of placebo-controlled trials when effective alternative therapy exists, regardless of the expected effect of the therapy. In part 1 of this paper, ethical arguments are addressed and the interpretive probl ems inherent in the use of active-control equivalence trials to establish e fficacy of a new treatment are clarified. However, uncertainties may compli cate decisions about appropriate use of placebo controls in some situations . Part 2 discusses more fully the ethical considerations for using placebo controls in particular medical settings. The value and relevance of placebo -controlled trials of new agents in situations in which proven effective th erapy is available are also explored.